Thermal dye sublimination transfer receiving element

Dye-image receiving element for use according to thermal dye sublimation transfer comprising a dye-image receiving layer, said dye-image receiving layer and/or a toplayer provided on top of said dye-image receiving layer (if such toplayer is present) containing a reaction product obtained by crosslinking and curing a non-polymeric compound containing two or more active hydrogen-containing radicals and a compound containing two or more isocyanate groups.

DESCRIPTION 
The present invention relates to dye-image receiving elements for use 
according to thermal dye sublimation transfer. 
Thermal dye sublimation transfer also called thermal dye diffusion transfer 
is a recording method in which a dye-donor element provided with a dye 
layer containing sublimable dyes having heat transferability is brought 
into contact with a dye-image receiving element and selectively, in 
accordance with a pattern information signal, heated with a thermal 
printing head provided with a plurality of juxtaposed heat-generating 
resistors, whereby dye from the selectively heated regions of the 
dye-donor element is transferred to the dye-image receiving element and 
forms a pattern thereon, the shape and density of which is in accordance 
with the pattern and intensity of heat applied to the dye-donor element. 
A dye-image receiving element for use according to thermal dye sublimation 
transfer usually comprises a support, e.g. paper or a transparant film, 
coated with a dye-image receiving layer, into which the dye can diffuse 
more readily. An adhesive layer may be provided between the support and 
the receiving layer. 
The dye-image receiving layer may comprise as binder, for example, a 
polycarbonate, a polyurethane, a polyester, a polyamide, a polyvinyl 
chloride, a polystyrene-co-acrylonitrile, a polycaprolactone or mixtures 
thereof. 
A disadvantage of using such a conventional dye receiving layer is the poor 
releasability, i.e., when the donor element and the receiving element are 
peeled apart after the heat transfer has been effected, the donor layer 
adheres to the receiving layer and thus is peeled to be transferred 
thereonto, whereby both the sheets will not be fit for use. 
In order to improve the releasability it has been proposed to use a 
cross-linked, cured dye receiving layer. Such receiving layers are 
described in, for example, EP 394460 and JP 90/95891. 
It has also been proposed to use a cross-linked cured layer on top of the 
receiving layer. Such a cured toplayer is described in EP 349141. 
These known cured receiving layer and toplayers are obtained by 
crosslinking and curing a resin having a cross-linkable reactive group and 
an additive having a cross-linkable reactive group. The crosslinkable 
reactive group may be a thermosetting reactive group or an ultraviolet- or 
electron beam-curing reactive group. In case curing is performed by the 
action of heat preference is given to resins containing an OH or NH.sub.2 
radical and an isocyanate additive. 
A disadvantage of heat-cured layers obtained by reaction of resins 
containing a cross-linkable reactive group and an isocyanate compound is 
the slowness of the curing reaction and the time needed to obtain complete 
curing of the matrix. The curing reaction is usually carried out by 
heating at a temperature of about 120.degree. C. to about 160.degree. C. 
for 10 to 60 minutes. To accelerate the reaction it is customary to add a 
catalyst to the curable composition. 
Furthermore when using a layer obtained by reaction between a resin 
containing a cross-linkable reactive group and an isocyanate compound 
curing is effected over the whole thickness of the layer while it is 
preferred to obtain curing only in the top region of the layer in order to 
improve releasability. 
It is an object of the present invention to provide a cured dye-image 
receiving element of excellent dyeability and releasability. 
It is another object of the present invention to provide a cured dye-image 
receiving element that is rapidly and easily obtained without the need of 
using a catalyst. 
It is a further object of the present invention to provide a cured 
dye-image receiving element with preferential curing at the surface of the 
layer. 
Other objects will become apparent from the description hereinafter. 
In accordance with the present invention a dye-image receiving element for 
use according to thermal dye sublimation transfer is provided, said 
dye-image receiving element comprising a dye-image receiving layer, 
characterized in that said dye-image receiving layer and/or a toplayer 
provided on top of said dye-image receiving layer (if such toplayer is 
present) contains a reaction product obtained by crosslinking and curing a 
non-polymeric compound containing two or more active hydrogen-containing 
radicals and a compound containing two or more isocyanate groups. 
Such dye image receiving elements are comparable to the known heat-cured 
dye image receiving elements obtained by crosslinking and curing a resin 
containing a crosslinkable reactive group and an isocyanate compound 
regarding dyeability and releasability. 
The non-polymeric compounds used according to the present invention are low 
molecular weight compounds preferably having a molecular weight less than 
1500 and most preferably less than 1000. They include oligomers containing 
not more than four recurring units. 
Non-polymeric compounds containing active hydrogen-containing radicals are 
more reactive than resins containing such radicals. This leads to an 
acceleration of the curing reaction: the curing takes place within the 
time needed to dry the layer and it is not necessary to further heat the 
layer after it is dried as is the case when resins containing such 
radicals are used. 
Further, the non-polymeric compounds containing active hydrogen-containing 
radicals can be added in excess to the compound containing isocyanate 
groups and this leads to a more complete curing reaction. The excess of 
non-polymeric compound can be evaporated afterwards, if it is sufficiently 
volatile. 
A further advantage of using non-polymeric compounds instead of resins is 
the possibility of selectively curing the surface of the layer. 
The non-polymeric compound containing the active hydrogen-containing 
radicals and the compound containing isocyanate groups can be provided in 
one single layer and cured. In this case the curing takes place 
substantially over the whole thickness of the layer. 
It is also possible to provide the non-polymeric compound containing active 
hydrogen-containing radicals in the layer to be cured and the compound 
containing isocyanate groups in a separate layer on top hereof, or vice 
versa. During drying of said layers reaction takes place between the 
non-polymeric compound containing active hydrogen-containing radicals and 
the compound containing isocyanate groups. In this case curing is effected 
preferentially on the surface of the layer to be cured. 
The polyisocyanate compound used in the present invention is a compound 
having at least two isocyanate groups. Diisocyanates, triisocyanates or 
mixtures hereof are preferred. Aliphatic, cycloaliphatic, araliphatic and 
aromatic polyisocyanates may be used. Mixtures of these polyisocyanates 
may also be used. 
Examples of such polyisocyanate compounds include ethylene diisocyanate; 
1,6-hexamethylene diisocyanate; isophorone diisocyanate; 
cyclohexane-1,4-diisocyanate; 4,4'-dicyclohexylmethane diisocyanate; 
p-xylylene diisocyanate; 1,4-phenylene diisocyanate; 2,4-toluene 
diisocyanate; 2,6-toluene diisocyanate; 4,4'-diphenylmethane diisocyanate; 
2,4'-diphenylmethane diisocyanate; polymethylene polyphenyl 
polyisocyanate; 1,5-naphthylene diisocyanate; triphenylmethane 
triisocyanate and Alpha,Omega-diisocyanate dimethylsiloxane. Of the above 
compounds 4,4'-diphenylmethane diisocyanate is preferred. 
Further polyisocyanates which have been modified by the introduction of 
urethane, allophanate, urea, bioret, isocyanurate (trimer), carbodiimide, 
uretonimine, uretdion or oxadiazintrion residues can be used. In this case 
compounds are formed with various numbers of isocyanate groups such as 
two, three, four or more isocyanate groups. Examples hereof are the 
following compounds: Desmodur L, Desmodur HL, Desmodur N, Desmodur IL, 
Desmodur VL, Desmodur Z-types. Desmodur W. Desmodur 15, Desmodur AP, 
Desmodur E-types, Desmodur BL 1100 (all supplied by Bayer) and the 
compounds described in Journal of Coatings Technology, Vol. 59, No. 749 
(1987), page 63-72. Of the above compounds Desmodur VL is preferred. 
The compounds containing the active hydrogen-containing radicals are 
compounds containing two or more of the following functional radicals 
(which may be the same or different): --NH.sub.2, --NH--, --NH--NH.sub.2 
--NH--NH--, --NH--OH, .dbd.N--OH, .dbd.N--NH.sub.2, --NH--CO--NH--, 
--NH--CO--N&lt;, --NH--COO--, --NH--CO--, --NH--SO.sub.2, --COOH, --OH and 
--SH. As compounds containing the same or different active 
hydrogen-containing functional groups di- tri-, tetra-, penta-, hexa- and 
possibly higher functional compounds can be used. Mixtures of such 
compounds can also be used. 
As such multifunctional non-polymeric compounds containing said active 
hydrogen-containing radicals there can be mentioned: amines, alcohols and 
phenols, carboxylic acids, hydroxy-carboxylic acids, amino-carboxylic 
acids, hydroxy-amino compounds, etc. 
Examples of compounds containing two or more --NH-- and/or --NH.sub.2 
radicals for use according to the present invention include ethylene 
diamine; diethylene diamine; hexamethylene diamine: p-phenylene diamine; 
tricyclodecyl diamine; tetramethylene 
N,N'-bis-(Gamma-amino-propyl)diamine; diethylene triamine; dodecyl 
diethylene triamine; diethylene 
N,N"-bis-(1-ethyl-3-methyl-pentyl)triamine; dipropylene triamine; 
triethylene tetramine; tetraethylene tetramine mono(undecyl)carbonamide; 
tetraethylene pentamine; pentaethylene hexamine; 
di(Epsilon-amino-amyl)amine; di-(Delta-amino-butyl)-amine; Jeffamine; 
diamino anisole; p,p-diaminodiphenyl sulfon; 1,2,3-triaminobenzene; 
1,3-diamino-2-(Beta-aminoethyl)benzene; p,p-diaminodiphenyl methane; 
1,1,1-tri-(aminomethyl)-ethane and 4,4'-diamino-dicyclohexyl-methane. 
Examples of compounds containing two or more -OH radicals for use according 
to the present invention include ethylene glycol; diethylene glycol; 
triethylene glycol; neopentylglycol; 1,2-propanediol; 1,3-propanediol; 
N,N-di(n-decyl)amino-2,3-propanediol; 1,4-butanediol; 
3-hydroxymethyl-2,4-pentanediol; 1,2-hexanediol; 1,6-hexanediol; 
1,4-cyclohexanediol; 1,8-octanediol; 1,2-octanediol; 1,9-nonanediol; 
1,2-decanediol; 1,10-decanediol; 1,11-undecanediol; 1,12-dodecanediol; 
1,2-dodecanediol; 1,13-tridecanediol; 1,14-tetradecanediol; 
1,15-pentadecanediol; 1,2-hexadecanediol; 1,16-hexadecanediol; 
1,17-heptadecanediol; 1,12-octadecanediol; 1,4-octadecanediol; 
1,18-octadecanediol; 1,2-epoxyoctadecanediol; 9-octadecene-1,12-diol; 
1,19-nonadecanediol; 1,20-eicosanediol; 1,21-heneicosanediol; 
1,22-docosanediol; 1,25-pentacosanediol; 1,2,4-butanetriol; 
1,2,6-hexanetriol; 1,2,2-trimethylol-ethane; 1,1,1-trimethylol-ethane; 
2,2'-bis(4-hydroxy-cyclohexyl)propane; 1,1,1-tri(hydroxymethyl)propane; 
trimethylolpropane; 1,4-dihydroxy-2-(hydroxymethylene)pentane; 
1,2,5-trihydroxypentane; pentahydroxypentane; 
4,4-bis(4-hydroxyphenyl)-l-n-dodecane; 
2,2,5,5-tetramethylol-cyclopentanol; 2,2,6,6-tetramethylol-cyclohexanol; 
1,4-cyclohexane dimethanol; tri-isopropanolamine, tri-ethanolamine; 
diethanolamino methylol; diethanolamino 2-propanol; methylamine 
monoethanol mono(2,3-dihydroxypropyl); xylitol; Bisphenol A; glycerine; 
glycerine mono stearate; glycerine mono oleate; glycerine mono 
ricinoleate; glycerine mono laurate; glycerine mono caprylate; 
pentaerytritol; dipentaerytritol; pentaerytritol distearate; 
meso-erytritol; N,N-di(hydroxyethyl)stearic amide; tetraethylene pentamine 
heptaethanol; tetraethylene pentamine hepta(N,N-diethanol)amine 
2-hydroxypropylene; ethylenediamine tetra(2,3-dihydroxypropane); 
ethylenediamine tetra(2-hydroxypropyl); 1,3-propylenediamine 
tetra(2-hydroxypropyl); ethylenediamine tetra(Beta-hydroxyethane); 
ethylenediamine monohydroxyethyl tri(2-hydroxypropyl); 1,3,5-trihydroxy 
benzene; 1,2,3-trihydroxy benzene; 1,2,4-trihydroxy benzene; 
1,2,3-trihydroxy-6-t-butyl benzene; 2,4,6-trihydroxy toluene; 
hydroquinone; 2,3-di(hydroxymethyl)-5-octadecyl hydroquinone; 
2,5-di(hydroxymethyl) hydroquinone; catechol; 4,6-di-t-butyl-catechol; 
4,4'-(2,3-dimethyl-tetramethylene) di-pyrocatechol; resorcin; 
2-nitro-resorcinol; 4-n-dodecylresorcinol; 2,4-dihydroxy acetophenone; 
3,4-dihydroxy benzaldehyde; heptadecyl-2,4-dihydroxyphenyl-ketone; cardol; 
dimer fatty alcohols; sorbitan fatty acid esters (e.g., sorbitan stearate, 
sorbitan oleate and sorbitan palmitate); carbohydrates such as glucose, 
galactose, saccharose, mannose, xylose, arabinose, maltose, lactose 
monohydrate, ribose, fructose, sorbitol, hematoxyline, mannite, ascorbic 
acid, dehydro-ascorbic acid; arboroles as described in Journal of the 
American Chemical Society (1990), Vol. 112, pages 8458 to 8465 such as 
compounds ARB1 and ARB2 as shown below. 
EQU ((HOCH.sub.2 --).sub.3 C--NH--CO).sub.2 --CH--CH.sub.2 
--CH--(CO--NH--C(--CH.sub.2 OH).sub.3).sub.2 ARB 1 
EQU ((HOCH.sub.2 --).sub.3 C--NH--CO).sub.2 --CH--(CH.sub.2).sub.10 
--CH--(CO--NH--C(--CH.sub.2 OH).sub.3).sub.2 ARB 2 
Examples of compounds containing two or more --COOH radicals for use 
according to the present invention include glutaric acid; itaconic acid; 
maleic acid; adipic acid; sebacic acid; azelaic acid; 1,4-cyclohexane 
dicarboxylic acid; decane dicarboxylic acid; undecane dicarboxylic acid; 
dodecane dicarboxylic acid; tridecane dicarboxylic acid: tetradecane 
dicarboxylic acid; heptadecane dicarboxylic acid; octadecane dicarboxylic 
acid; nonadecane dicarboxylic acid; eicosane dicarboxylic acid; docosane 
dicarboxylic acid; malonic acid; tetradecylmalonic acid; hexadecylmalonic 
acid; octadecylmalonic acid; diheptylmalonic acid; succinic acid; 
octylsuccinic acid; decylsuccinic acid; dodecylsuccinic acid; 
tetradecylsuccinic acid; hexadecylsuccinic acid; octadecylsuccinic acid; 
octenylsuccinic acid; iso-octenylsuccinic acid; decenylsuccinic acid; 
dodecenylsuccinic acid; tetradecenylsuccinic acid; hexadecenylsuccinic 
acid; octadecenylsuccinic acid; docosylsuccinic acid; docosenylsuccinic 
acid; tetrapropenylsuccinic acid; triacontenylsuccinic acid; 
polyisobutenylsuccinic acid; nonadecane-1,2,3-tricarboxylic acid; 
nonadecane-1,3,3-tricarboxylic acid; octadecane-1,1,2-tricarboxylic acid; 
octadecane-1,2,2-tricarboxylic acid; heptadecane-1,2,3-tricarboxylic acid; 
heptadecane-1,3,3-tricarboxylic acid; hexadecane-1,1,2-tricarboxylic acid; 
heptane-1,2,3-tricarboxylic acid; propane-1,2,3-tricarboxylic acid; 
butane-1,2,4-tricarboxylic acid; nonadecane-1,2,3,3-tetracarboxylic acid; 
1,2,3,4-tetracarboxybutane; 1,1,12,12-tetracarboxydodecane; 
1,2,3,4,5,5-hexa-(Beta-carboxyethyl) cyclopentadiene; benzene 
1,3,5-tricarboxylic acid; benzene 1,2,3-tricarboxylic acid; benzene 
1,2,4-tricarboxylic acid; benzene 1,2,4,5-tetracarboxylic acid; benzene 
hexacarboxylic acid; nitrilo-triacetic acid; ethylene diamine triacetic 
acid mono(l-octadecanoic acid); N,N'-p-phenylene diamine tetracetic acid; 
1,2-diamino cyclohexane tetracetic acid; ethyleneglycol bis(2-aminoethyl) 
tetracetic acid; ethylene diamine tetracetic acid; hexamethylene diamine 
tetracetic acid; 1,2-propylene diamine tetracetic acid; 1,3-propylene 
diamine tetracetic acid; diethylene triamine pentacetic acid; triethylene 
tetraamine hexacetic acid; tetraethylene pentaamine heptacetic acid; 
nitrilo tripropionic acid; dimer fatty acids and derivatives such as 
PRIPOL 1008/1009 (CAS registry no. 68783-41-5) which is a mixture of 
aromatic, cycloaliphatic and aliphatic C.sub.36 dimer fatty acid isomers 
and PRIPLAST 3008 (CAS registry no. 68956-10-5) which is the dimethyl 
ester of said dimer acid, PRIPOL 1004 which is a C.sub.44 dimer fatty acid 
(all supplied by Unichema), EMPOL supplied by Quantum Chemicals which is a 
C.sub.36 aliphatic dimer acid and UNIDYME 14 and UNIDYME 60 supplied by 
Union Camp. 
Examples of compounds containing two or more different active 
hydrogen-containing radicals for use according to the present invention 
include N-hydroxyethylethylene diamine; ethylene diamine 
N,N'-di(2-hydroxy-3-diethanolamine-propylene); ethylene diamine 
monoethanol; 1,3-propylene diamine monoethanol; ethylene diamine 
N,N'-diethanol; p-phenylene diamine N,N-diethanol; ethylene diamine 
monopropanol; ethylene diamine N,N'-di-isopropanol; 1,3-diamino 
2-propanol; 1,2-diamino 3-propanol; 3-amino-2',4'-dihydroxy-benzophenone; 
salicylic acid; acetylsalicylic acid; diethanol mono(acetic acid)amine; 
resorcine-2,4-dicarboxylic acid; 2,5-di-hydroxy-terephthalic acid; 
3-(3,4-dihydroxyphenyl)-propionic acid; hydroxybenzoic acid; 
3,5-dihydroxybenzoic acid; 2.5-dihydroxybenzoic acid; 2,6-dihydroxybenzoic 
acid; 2,4-dihydroxybenzoic acid; 2,3-dihydroxybenzoic acid; 
3,4-dihydroxybenzoic acid; 2,3-dihydroxy-4-(Beta-hydroxyethoxy) benzoic 
acid; 2,4,6-trihydroxy-benzoic acid; 3,4,5-trihydroxy-benzoic acid; 
2,4,5-trihydroxy-benzoic acid; 2,3,4-trihydroxy-benzoic acid; 
2,5-di-propionic acid hydroquinone; 2-(Gamma-carboxy-propyl)-hydroquinone; 
2-carboxy-5-methyl-hydroquinone; diethylene-triamine-monoacetic 
acid-monododecyl; ethylene-diamine-N,N'-diacetic acid; 
ethylene-diamine-N,N-diacetic acid; tetraethylene-pentaamine-diacetic 
acid; 1,3-propylene-diamine-N,N'-dipropionic acid; 
dipropylene-triamine-N,N'-dipropionic acid; 4,6-diamino-iso-phthalic acid; 
1,3-propylene-diamine-N-(2-methyl-butanoic acid)-N'-dodecyl; 
ethylenediamine-mono(l-octadecanoic acid); 11-amino-undecanoic acid; 
12-amino-dodecanoic acid; 1-glutaminic acid; Alpha-amino-pelargonic acid; 
Alpha-amino-pentane carboxylic acid; Omega-amino-capronic acid; 
amino-succinic acid; 4-amino-butyric acid; 4-amino-cyclohexane carboxylic 
acid; aminoacids such as glycine, alanine, valine, leucine, isoleucine, 
phenylalanine, proline, methionine, serine, threonine, tyrosine, lysine, 
hydroxylysine, arginine, histidine, asparaginic acid, glutaminic acid, 
N-methyl-D-glucosamine; diacetic acid-mono-ethanolamine; 
ethylene-diamine-N,N'-diethanol-N,N'-diacetic acid; 
(trimethanol)methylene-amine-diacetic acid; ethylene-diamine-triacetic 
acid-monoethanol; 1,3-diamino-2-propanol-tetraacetic acid; 
2,5-di(2-hydroxyethylamino)-terephthalic acid. 
The non-polymeric compound containing the active hydrogen-containing 
radicals used according to the present invention can further contain other 
non-reactive groups such as nitro, halogen, ketone, aldehyde, sulfonate, 
sulfone, phosphate, ester or ether groups. 
The non-polymeric compound containing the active hydrogen-containing 
radicals can further contain a functional group that imparts to the 
receiving element, for example, a stabilizing, plasticizing, releasing, 
glossy or mat effect. 
Examples of such compounds that incorporate besides the active 
hydrogen-containing radicals also an antioxidising group are listed below. 
##STR1## 
The amount of non-polymeric compound containing active hydrogen-containing 
radicals and the amount of compound containing isocyanate groups is 
preferably such that the mole ratio of NCO/active hydrogen-containing 
radical is between 2/1 and 1/10 and preferably between 1/1 and 1/5. 
The cured layer according to the present invention may be formed by 
providing a composition for forming the layer by dissolving or dispersing 
the non-polymeric compound and the polyisocyanate compound (and optionally 
other additives) in a solvent and coating that composition on a support by 
suitable means followed by drying. During the drying step (1 to 2 minutes 
at 1200.degree. C.) crosslinking and curing takes place. After drying a 
post heating step (1 to 5 minutes at 120.degree. C.) may be carried out so 
as to obtain a still higher degree of crosslinking. Due to the high 
mobility of the non-polymeric compound in the dried layer the curing 
reaction can further continue at room temperature, thereby avoiding the 
need for a post heating step. 
One of the reaction partners can initially be present in another layer. For 
example the cured layer is formed by coating a composition containing the 
non-polymeric compound (and optionally other additives) on the support 
followed by drying. Subsequently a composition containing the isocyanate 
compound (and optionally other additives) is coated on top of this layer 
and dried. A post heating step (1 to 5 minutes at 120.degree. C.) may be 
carried out. This can also be carried out vice versa, namely with the 
isocyanate compound in the receiving layer and the non-polymeric compound 
in the toplayer. 
In order to further accelerate the curing reaction between the 
non-polymeric compound and the polyisocyanate compound in accordance with 
the present invention a catalyst may be added. Catalysts used to this end 
include tertiary amines (e.g. triethylamine) and organic metallic 
compounds. 
Especially organometallic compounds based on dibutyltin or dioctyltin are 
generally used. Examples of catalysts based on dibutyltin include 
dibutyltin dilaurate, dibutyltin oxide, dibutyltin dichloride, dibutyltin 
di-2-ethylhexyl thioglycolate, dibutyltin di(monobutyl) maleate, 
dibutyltin di(monononyl) maleate, dibutyltin diacetate, dibutyltin 
mercaptide, dibutyltin Beta-mercaptopropionate, dibutyltin thiocarboxylate 
and dibutyltin di-2-ethylhexoate. Examples of catalysts based on 
dioctyltin include dioctyltin dilaurate, dioctyltin thioglycolate, 
dioctyltin Beta-mercaptopropionate, 
dioctyltin-1,4-butanediol-bis(mercaptoacetate), dioctyltin ethylene glycol 
thioglycolate, dioctyltin thiocarboxylate, dioctyltin maleate, dioctyltin 
maleate polymer, dioctyltin-(1,2-propylene glycol maleate), 
dioctyltin-di-(monobutyl) maleate, dioctyltin-bis-(2-ethylhexyl maleate), 
dioctyltin-bis-(lauryl thioglycolate), dioctyltin oxide, dioctyltin 
dichloride, mono-octyltin dichloride and trioctyltin dichloride. 
Other organometallic compounds, which may be used as catalysts in 
accordance with the present invention include stannous octoate, lead 
octoate, cobalt naphthenate, stannous chloride, stannic chloride, 
tetra-n-butyltin, tetraphenyltin, trimethyltin hydroxide and 
dimethyl-2-tin chloride. 
Particular preference is given to dibutyltin dilaurate. 
In the case of a cured toplayer according to the present invention a binder 
is not necessary but may be used. Examples of binders that may be used in 
such a toplayer are nitrocellulose, styrene copolymers, polyesters, 
polycarbonates and co-vinylchloride-vinylacetates. 
In the case of a cured dye receiving layer according to the present 
invention it is necessary to include a binder in said layer. 
As binder there can be used any binder known in dye receiving layers of 
thermal transfer materials, for example, polyesters such as described in 
European patent applications nos 90202759 and 90202760, solvent soluble 
polyesters such as VYLON supplied by Toyobo, DYNAPOL supplied by Huls 
Chemie and VITEL supplied by Goodyear, co-vinylchloride-vinylacetates such 
as VINYLITE and UCAR types VYNS-3, VYHH, VYHD and VYLF supplied by Union 
Carbide, polycarbonates, polyurethanes, styrene copolymers (e.g. 
co-styrene-acrylonitrile), polyamides. etc. Examples of such resins are 
described in, e.g., EP 133011, EP 133012, EP 144247, EP 227094 and EP 
22806 6. Mixtures of these resins can also be used. 
The amount of binder used in the dye receiving layer of the present 
invention is from 50 to 95% by weight, preferably about 80% by weight. 
The dye receiving layer of the present invention can contain as binder a 
resin containing active hydrogen-containing radicals that is then cured 
together with the non-polymeric compound and the polyisocyanate compound 
used in accordance with the present invention. These resins may include 
polyester resins, acrylic resins, vinyl resins, polyurethane resins, 
cellulosic resins. polysaccharides, which are modified by introducing into 
their molecular chains one or more active hydrogen radicals. These resins 
may be used alone or in a combination of two or more of such resins or 
they can be used in combination with a conventional binder for a receiving 
layer as listed above. 
Examples of such isocyanate curable resins are: vinyl chloride/vinyl 
acetate copolymers modified with vinyl alcohol or hydroxyalkylacrylate or 
maleic acid or epoxy (e.g. the UCAR type resins VMCH, VMCC, VMCA, VAGH, 
VAGD, VAGF, VAGC, VYNC, VROH, VYES, VYES-4, VP-200 and VERR-40 supplied by 
Union Carbide); linear or branched polyesters or polyethers or 
polyacrylates containing an OH radical such as the Desmophen types 550 U. 
651, 670, 690, 800, 1200, 1700, 1800, RD 181 supplied by Bayer; cellulose 
derivatives and gelatine. 
These isocyanate curable resins are also suitable for forming on themselves 
together with a polyisocyanate compound a cured dye-receiving layer (i.e. 
without a non-polymeric compound containing active hydrogen-containing 
radicals). The ratio equivalent NCO/ active hydrogen is for these systems 
preferably between 0.1 and 2 and the weight percentage of active hydrogen 
in the resin (or resin mixture) is between 0.05 and 1 wt % (e.g. for OH 
radical between 0.85 and 17 wt %). The composition of such dye receiving 
element regarding optional additives, intermediate layers, support 
material, etc. can be as is set forth hereinafter for the curable dye 
receiving element of the present invention. 
The heat-curable system of the present invention based on isocyanate and 
non-polymeric compounds containing active hydrogen-containing radicals can 
also be used in combination with a heat-curable system based on isocyanate 
and particles containing active hydrogen-containing radicals, preferably 
at the surface of said particles, e.g. the silica organosols marketed 
under the tradename HIGHLINK OG by Hoechst which are non-agglomerated 
colloidal silica particles modified by functional organic molecules. 
These isocyanate curable particles are also suitable for forming on 
themselves together with a polyisocyanate compound a cured dye-receiving 
layer (i.e. without a non-polymeric compound containing active 
hydrogen-containing radicals). The composition of such dye receiving 
element regarding optional additives, intermediate layers, support 
material, etc. can be as is set forth hereinafter for the curable dye 
receiving element of the present invention. 
The heat-curable system of the present invention based on isocyanate and 
non-polymeric compound containing active hydrogen-containing radicals can 
also be used in combination with another heat-curable system. 
Examples of such other heat-curable systems that can be used in such 
combination are: heat-curable systems based on carbamoylpyridinium salts 
(and derivatives thereof of the type described in U.S. Pat. No. 3880665 
and U.S. Pat. No. 4063952 ) and compounds containing carboxyl and amino 
radicals (non-polymeric compounds and/or resins e.g. gelatine); 
heat-curable systems based on the reaction between amino. carboxyl, 
aldehyde (or ketone) and isonitrite compounds i.e. the reaction known as 
the 4 Compound Condensation (4CC) reaction as described by Ugi in 
Intrascience Chemistry Reports (1971). Vol. 3, page 229, in Angew. Chem. 
(1962), Vol. 74, page 9, and in Neuere Methoden der prgparativen Org. 
Chemie, Foerst Verlag Chemie, Vol. 4, page 1; heat-curable systems based 
on the reaction between vinylsulfones and compounds containing amino 
radicals (non-polymeric compounds or resins). 
These heat-curable systems are also suitable for forming a cured 
dye-receiving layer or toplayer on themselves (i.e. not in combination 
with the heat-curable system of the present invention based on isocyanate 
and non-polymeric compound containing active hydrogen-containing 
radicals). The composition of such dye receiving element regarding 
optional additives, intermediate layers, support material, etc. can be as 
is set forth hereinafter for the curable dye receiving element of the 
present invention. 
A release agent containing a crosslinkable reactive group may also be 
incorporated as a part of the material forming the cured layer. These 
release agents may include silicone, fluorine, long-chain aliphatic 
hydrocarbon compounds, waxes and other like substances , which are 
modified by introducing into their molecular chains one or more active 
hydrogen-containing radicals. In this case the release agent, the 
non-polymeric compound and the polyisocyanate compound are crosslinked and 
cured in combination. Examples of such release agents are amino modified 
silicone oil and epoxy modified silicone oil. 
High boiling organic solvents or thermal solvents or plasticizers can be 
included in the image-receiving layer, as substances which can accept or 
dissolve the dyes or as diffusion promotors for the dyes. Useful examples 
of such high boiling organic solvents and thermal solvents include the 
compounds disclosed in, for example, JP 62/174754, JP 62/245253, JP 
61/209444, JP 61/200538, JP 62/8145, JP 62/9348, JP 62/302 47, JP 
62/136646. 
For the purpose of improving the whiteness of the receiving layer to 
enhance sharpness of the transferred image and also imparting writability 
to the receiving surface as well as preventing retransfer of the 
transferred image, a white pigment can be added to the receiving layer. As 
white pigment, titanium oxide, zinc oxide, kaolin, clay, calcium 
carbonate, fine powdery silica, etc. can be employed, and these can be 
used as a mixture of two or more kinds as described above. 
Also, for further enhancing the light resistance of the transferred image, 
one or two or more kinds of additives such as UV-ray absorbers, light 
stabilizers and antioxidants, can be added, if necessary. The amounts of 
these UV-ray absorbers and light stabilizers is preferably 0.05 to 10 
parts by weight and 0.5 to 3 parts by weight, respectively, per 100 parts 
of the resin constituting the receiving layer. 
The dye receiving element of the present invention can contain a release 
agent (in the receiving layer or the toplayer) for improvement of the 
release property with respect to the donor element. As the release agent, 
solid waxes such as polyethylene wax, amide wax, and Teflon powder; 
fluorine based and phosphate ester based surfactants; and paraffin based, 
silicone based and fluorine based oils. Silicone oils, preferably reactive 
silicone oils and silicone containing copolymers such as a 
polysiloxane-polyether copolymer and blockcopolymers, are preferred (e.g. 
TEGOGLIDE supplied by Goldschmidt and SILWET supplied by Union Carbide. 
As the support for the receiver sheet it is possible to use a transparant 
film or sheet of various plastics such as polyethylene terephthalate, 
polyolefin, polyvinyl chloride, polystyrene, polycarbonate, polyether 
sulfone, polyamide, cellulose ester or polyvinyl alcohol-co-acetal. 
Blue-colored polyethylene terephthalate film can also be used. The support 
may also be a reflective support such as paper e.g. top quality paper, art 
paper, cellulose fiber paper; baryta-coated paper; polyolefin-coated paper 
e.g. dual polyethylene-coated paper; synthetic paper e.g. polyolefin type, 
polystyrene type or white polyester type i.e. white-pigmented polyester. 
Also, a laminated product by any desired combination of the above can be 
used. Typical examples of the laminates include a laminate of cellulose 
fiber paper and synthetic paper and a laminate of cellulose fiber paper 
and a plastic film or sheet. As further examples of the laminates, a 
plastic film can be used with synthetic paper instead of cellulose fiber 
paper. Further, a laminate of cellulose fiber paper, plastic film and 
synthetic paper can also be used. 
The support sheet serves to support the dye receiving layer, and it is 
desirable that the support sheet has mechanical strength sufficient enough 
to handle the dye receiving sheet which is heated at the time of heat 
transfer recording. If the dye-receiving layer alone has the necessary 
mechanical strength, the support sheet may be omitted. 
The dye-receiving layer of the present invention preferably has an overall 
thickness of from 0.5 to 50 um, more preferably from 2.5 to 10 um, when 
the dye-receiving layer is provided on a support sheet, or preferably from 
3 to 120 um when it is self-supporting i.e. a support sheet is omitted. 
The image receiving layer may be a single layer, or two or more such layers 
may be provided on the support. 
Also receiving layers may be formed on both surfaces of the support. In the 
case of a transparant support recto-verso printing on both receiving 
layers as described in European Patent Application No. 90200930.7 then 
leads to an increase in density of the transferred image. 
In case a toplayer is provided the thickness of such a toplayer is 
preferably 0.01 to 5 um, particularly 0.05 to 2 um. 
The image receiving element of the present invention may also have one or 
more intermediate layers between the support and the image receiving 
layer. Depending on the material from which they are formed, the 
intermediate layers may function as cushioning layers, porous layers or 
dye diffusion preventing layers, or may fulfill two or more of these 
functions, and they may also serve the purpose of an adhesive, depending 
on the particular application. 
The material constituting the intermediate layer may include, for example, 
an urethane resin, an acrylic resin, an ethylenic resin, a butadiene 
rubber, or an epoxy resin. The thickness of the intermediate layer is 
preferably from 2 to 20 um. 
Dye diffusion preventing layers are layers which prevent the dye from 
diffusing into the support. The binders used to form these layers may be 
water soluble or organic solvent soluble, but the use of water soluble 
binders is preferred, and especially gelatin is most desirable. 
Porous layers are layers which prevent the heat which is applied at the 
time of thermal transfer from diffusing from the image receiving layer to 
the support to ensure that the heat which has been applied is used 
efficiently. 
Fine powders consisting of silica, clay, talc, diatomaceous earth, calcium 
carbonate, calcium sulfate, barium sulfate, aluminum silicate, synthetic 
zeolites, zinc oxide, lithophone, titanium oxide or alumina for example, 
can be included in the image receiving layers, cushioning layers, porous 
layers, diffusion preventing layers and adhesive layers, etc. constituting 
the thermal transfer image receiving element of the present invention. 
Also, the image receiving element of the present invention can have 
antistatic treatment applied to the front or back surface thereof. Such 
antistatic treatment may be carried out by incorporating an antistatic 
agent in, for example, the image receiving layer which becomes the front 
surface or in an antistatic preventive layer applied to the image 
receiving surface. A similar treatment can also be effected to the back 
surface. By such treatment, mutual sliding between the image receiving 
sheets can be smoothly performed, and there is also the effect of 
preventing the attachment of dust on the image receiving sheet. 
Furthermore, the image receiving sheet can have a lubricating layer 
provided on the back surface of the sheet support. The material for the 
lubricating layer may include methacrylate resins such as methyl 
methacrylate, etc. or corresponding acrylate resins, vinyl resins such as 
vinyl chloride-vinyl acetate copolymer. 
The receiving element can have detection marks provided on one surface, 
preferably the back surface so that the receiving element can be 
accurately set at a desired position during transfer, whereby the image 
can be formed always at a correct desired position. 
For the formation of black thermal dye sublimation transfer images 
representing radiographic diagnostic information as described e.g. in 
European Patent Application no. 91200791.1 filed Apr. 5,1991, on 
transparant or blue-colored film support, said support may be provided 
before or during or after the sublimation transfer cycle with black 
margins or colored margins having a high density of at least two, 
surrounding the image area of only one image if only one image is 
reproduced or all of the image areas if a number of images is reproduced, 
in order to avoid glare at the edges impairing interpretation by the 
radiologist on the viewing illuminator. 
These black or colored margins can be provided in a number of ways. 
For example, during manufacturing of the support for the image receiving 
material the margins can be realised by printing either on the backside or 
receptor side of the support (offset, gravure, screen, flexo, 
electrophotographic or ionographic printing). The margins can be provided 
before or after cutting the support material into sheets. 
A special dye donor element comprising a separate area containing black or 
colored material can be used to provide said margins on the receptor 
element by heat, light and/or pressure during the sublimation transfer 
cycle. 
After sublimation transfer the margins can be provided sheet by sheet on 
the image receiving element by any of the printing processes referred to 
above. 
The margins when provided before sublimation transfer can be used not only 
to avoid undesirable glare but also to accurately set the image receiving 
element at a desired position during transfer printing. They can contain 
detection marks for this purpose. 
A dye-donor element for use according to thermal dye sublimation transfer 
in combination with the present receiving element usually comprises a very 
thin support e.g. a polyester support, one side of which is covered with a 
dye layer, which contains the printing dyes. Usually an adhesive or 
subbing layer is provided between the support and the dye layer. Normally 
the opposite side is covered with a slipping layer that provides a 
lubricated surface against which the thermal printing head can pass 
without suffering abrasion. An adhesive layer may be provided between the 
support and the slipping layer. 
The dye layer can be a monochrome dye layer or it may comprise sequential 
repeating areas of different colored dyes like e.g. of cyan, magenta, 
yellow and optionally black hue. When a dye-donor element containing three 
or more primary color dyes is used, a multicolor image can be obtained by 
sequentially performing the dye transfer process steps for each color. 
The dye layer of such a thermal dye sublimation transfer donor element is 
formed preferably by adding the dyes, the polymeric binder medium, and 
other optional components to a suitable solvent or solvent mixture, 
dissolving or dispersing the ingredients to form a coating composition 
that is applied to a support, which may have been provided first with an 
adhesive or subbing layer, and dried. 
The dye layer thus formed has a thickness of about 0.2 to 5.0 um, 
preferably 0.4 to 2.0 um, and the ratio of dye to binder is between 9:1 
and 1:3 by weight, preferably between 2:1 and 1:2 by weight. 
As polymeric binder the following can be used: cellulose derivatives, such 
as ethyl cellulose, hydroxyethyl cellulose, ethylhydroxy cellulose, 
ethylhydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, 
nitrocellulose, cellulose acetate formate, cellulose acetate hydrogen 
phthalate, cellulose acetate, cellulose acetate propionate, cellulose 
acetate butyrate, cellulose acetate pentanoate, cellulose acetate 
benzoate, cellulose triacetate; vinyl-type resins and derivatives, such as 
polyvinyl alcohol, polyvinyl acetate, polyvinyl butyral, copolyvinyl 
butyral-vinyl acetal-vinyl alcohol, polyvinyl pyrrolidone, polyvinyl 
acetoacetal, polyacrylamide; polymers and copolymers derived from 
acrylates and acrylate derivatives, such as polyacrylic acid, polymethyl 
methacrylate and styrene-acrylate copolymers; polyester resins; 
polycarbonates; copolystyrene-acrylonitrile; polysulfones; polyphenylene 
oxide; organosilicones, such as polysiloxanes; epoxy resins and natural 
resins, such as gum arabic. Preferably cellulose acetate butyrate or 
copolystyrene-acrylonitrile(-butadieen) is used as binder for the dye 
layer. 
Any dye can be used in such a dye layer provided it is easily transferable 
to the dye-image-receiving layer of the receiver sheet by the action of 
heat. 
Typical and specific examples of dyes for use in thermal dye sublimation 
transfer have been described in, e.g.. EP 453020, EP 209990, EP 209991, EP 
216483, EP 218397, EP 227095, EP 227096, EP 229374, EP 235939, EP 247737, 
EP 257577, EP 257580. EP 258856, EP 279330, EP 279467, EP 285665, EP 
400706, U.S. Pat. No. 4743582, U.S. Pat. No. 4753922, U.S. Pat. No. 
4753923, U.S. Pat. No. 4757046, U.S. Pat. No. 4769360, U.S. Pat. No. 
4771035, JP 84/78894, JP 84/78895, JP 84/78896, JP 84/227490, JP 
84/227948, JP 85/27594, JP 85/30391 . JP 85/229787, JP 85/229789, JP 
85/229790, JP 85/229791, JP 85/229792, JP 85/229793. JP 85/229795, JP 
86/41596, JP 86/268493, JP 86/268494, JP 86/268495 and JP 86/284489. 
The coating layer may also contain other additives, such as curing agents, 
preservatives, organic or inorganic fine particles, dispersing agents, 
antistatic agents, defoaming agents, viscosity controlling agents, etc., 
these and other ingredients being described more fully in EP 133011, EP 
133012, EP 111004 and EP 279467. 
Any material can be used as the support for the dye-donor element provided 
it is dimensionally stable and capable of withstanding the temperatures 
involved, up to 4000.degree. C. over a period of up to 20 msec, and is yet 
thin enough to transmit heat applied on one side through to the dye on the 
other side to effect transfer to the receiver sheet within such short 
periods, typically from 1 to 10 msec. Such materials include polyesters 
such as polyethylene terephthalate, polyamides, polyacrylates, 
polycarbonates, cellulose esters, fluorinated polymers, polyethers, 
polyacetals, polyolefins, polyamides, glassine paper and condenser paper. 
Preference is given to a polyethylene terephthalate support. In general, 
the support has a thickness of 2 to 30 um. The support may also be coated 
with an adhesive or subbing layer, if desired. 
The dye layer of the dye-donor element may be coated on the support or 
printed thereon by a printing technique such as a gravure process. 
In order to obtain transferred images of high density, for example for 
obtaining a hard copy of a medical diagnostic image, a double-layered 
structure can be used for the dye layer, i.e. two dye layers containing 
dye(s) and binder(s) with the same or different dye/binder ratios and/or 
the same or different dyes and/or the same or different binders. 
A dye-barrier layer comprising a hydrophilic polymer may also be employed 
in the dye-donor element between its support and the dye layer to improve 
the dye transfer densities by preventing wrong-way transfer of dye towards 
the support. The dye barrier layer may contain any hydrophilic material 
which is useful for the intended purpose. In general, good results have 
been obtained with gelatin, polyacryl amide, polyisopropyl acrylamide, 
butyl methacrylate grafted gelatin, ethyl methacrylate grafted gelatin, 
ethyl acrylate grafted gelatin, cellulose monoacetate, methyl cellulose, 
polyvinyl alcohol, polyethylene imine, polyacrylic acid, a mixture of 
polyvinyl alcohol and polyvinyl acetate, a mixture of polyvinyl alcohol 
and polyacrylic acid or a mixture of cellulose monoacetate and polyacrylic 
acid. Suitable dye barrier layers have been described in e.g. EP 227091 
and EP 228065. Certain hydrophilic polymers, for example those described 
in EP 227091, also have an adequate adhesion to the support and the dye 
layer, thus eliminating the need for a separate adhesive or subbing layer. 
These particular hydrophilic polymers used in a single layer in the donor 
element thus perform a dual function, hence are referred to as 
dye-barrier/subbing layers. 
Preferably the reverse side of the dye-donor element can be coated with a 
slipping layer to prevent the printing head from sticking to the dye-donor 
element. Such a slipping layer would comprise a lubricating material such 
as a surface active agent, a liquid lubricant, a solid lubricant or 
mixtures thereof, with or without a polymeric binder. The surface active 
agents may be any agents known in the art such as carboxylates, 
sulfonates, phosphates, aliphatic amine salts, aliphatic quaternary 
ammonium salts, polyoxyethylene alkyl ethers, polyethylene glycol fatty 
acid esters, fluoroalkyl C.sub.2 -C.sub.20 aliphatic acids. Examples of 
liquid lubricants include silicone oils, synthetic oils, saturated 
hydrocarbons and glycols. Examples of solid lubricants include various 
higher alcohols such as stearyl alcohol, fatty acids and fatty acid 
esters. Suitable slipping layers are described in e.g. EP 138483, EP 
227090, U.S. Pat. No. 4567113, US 4572860, U.S. Pat. No. 4717711. 
Preferably the slipping layer comprises as binder a styrene-acrylonitrile 
copolymer or a styrene-acrylonitrile-butadiene copolymer or a mixture 
thereof and as lubricant in an amount of 0.1 to 10% by weight of the 
binder (mixture) a polysiloxane-polyether copolymer or 
polytetrafluoroethylene or a mixture thereof. 
The dye layer of the dye-donor element may also contain a releasing agent 
that aids in separating the dye-donor element from the dye-receiving 
element after transfer. The releasing agents can also be applied in a 
separate layer on at least part of the dye layer. For the releasing agent 
solid waxes, fluorine- or phosphate-containing surfactants and silicone 
oils are used. Suitable releasing agents are described in e.g. EP 133012, 
JP 85/19138, EP 227092. 
The dye-receiving elements according to the invention are used to form a 
dye transfer image. Such a process comprises placing the dye layer of the 
donor element in face-to-face relation with the dye-receiving layer of the 
receiver sheet and imagewise heating from the back of the donor element. 
The transfer of the dye is accomplished by heating for about several 
milliseconds at a temperature of 4000.degree. C. 
When the process is performed for but one single color, a monochrome dye 
transfer image is obtained. A multicolor image can be obtained by using a 
donor element containing three or more primary color dyes and sequentially 
performing the process steps described above for each color. The above 
sandwich of donor element and receiver sheet is formed on three occasions 
during the time when heat is applied by the thermal printing head. After 
the first dye has been transferred, the elements are peeled apart. A 
second dye-donor element (or another area of the donor element with a 
different dye area) is then brought in register with the dye-receiving 
element and the process repeated. The third color and optionally further 
colors are obtained in the same manner. 
In order to accomplish a perfect register when the process is performed for 
more than one color and in order to detect what color is existing at the 
printing portion of the donor element, detection marks are commonly 
provided on one surface of the donor element. Generally optically 
detectable marks are used that can be detected by a light source and a 
photo sensor; detection can be done by measuring the light transmitted 
through the detection mark or reflected from said mark. The marks being in 
the form of a light-absorbing or light-reflecting coating are formed in a 
preassigned position on the donor element by e.g. gravure printing. The 
detection marks can comprise an infrared absorbing compound such as carbon 
black. The detection mark can also comprise one of the image dyes that are 
used for the image formation, with the detection being in the visible 
range. 
In addition to thermal heads, laser light, infrared flash or heated pens 
can be used as the heat source for supplying heat energy. Thermal printing 
heads that can be used to transfer dye from the dye-donor elements of the 
present invention to a receiver sheet are commercially available. In case 
laser light is used, the dye layer or another layer of the dye element has 
to contain a compound that absorbs the light emitted by the laser and 
converts it into heat, e.g. carbon black. 
Alternatively, the support of the dye-donor element may be an electrically 
resistive ribbon consisting of, for example, a multi-layer structure of a 
carbon loaded polycarbonate coated with a thin aluminum film. Current is 
injected into the resistive ribbon by electrically adressing a print head 
electrode resulting in highly localized heating of the ribbon beneath the 
relevant electrode. The fact that in this case the heat is generated 
directly in the resistive ribbon and that it is thus the ribbon that gets 
hot leads to an inherent advantage in printing speed using the resistive 
ribbon/electrode head technology compared to the thermal head technology 
where the various elements of the thermal head get hot and must cool down 
before the head can move to the next printing position. 
The following examples are provided to illustrate the invention in more 
detail without limiting, however, the scope thereof.