EP0503439A1 - Dye receiver for the thermosublimation printing process - Google Patents

Abstract

When using a dye receptor for the thermosublimation printing process with a dye receptor layer which consists essentially of a polyurethane formed by crosslinking and is characterised in that the polyurethane contains at least 5% by weight of urethane groups (-O-CO-NH-), dye transfers of high dye density, excellent sharpness and good stability are obtained.

Description

The present invention relates to a color acceptor element for the thermal sublimation printing process.

There are a number of methods for printing out video or computer-stored images, of which the thermal sublimation printing process has proven to be superior in certain requirements due to its advantages over other processes. In this recording method, a sheet-like or ribbon-shaped donor material which contains a sublimable dye is brought into contact with a dye (dye) acceptor layer and heated imagewise to transfer the dye.

The thermal head is controlled and the dye is transferred from the donor ribbon to the receiving element in accordance with the stored template. A detailed description of the process can be found, for example, in "High Quality Image Recording by Sublimation Transfer Recording Material", Electronic Photography Association Documents 27 (2), 1988 and the literature cited therein. A particular advantage of this printing process is the ability to fine-tune color intensities.

Color acceptor elements for thermal sublimation printing usually include a backing, e.g. Paper or transparent films that are coated with the actual color acceptor layer. An adhesive layer can be applied between the base and the receiving layer.

Polymers from different classes of substances can be used as the material for the color acceptor layer.

Color acceptor layers with urethane groups have also become known (EP-A-0 234 563). However, the urethanes are only described here as a possible component which is usually combined with other thermoplastic polymers.

Crosslinked color acceptor layers based on polyhydroxyl compounds and polyisocyanates (EP-A-0 394 460) are also described, but the proportion of crosslinking urethane groups is low here. However, this does not achieve very high color densities.

The color acceptor layers currently available do not yet sufficiently meet the requirements for high color density, sufficient image stability and good resolution. It is particularly difficult to get high To achieve color density and sufficient image stability with minimal lateral diffusion.

The object of the invention was to provide a color acceptor element for the thermal sublimation printing process which does not have the disadvantages mentioned above.

It has been found that highly crosslinked polyurethane coatings, which are largely inert to chemical influences, are suitable for absorbing the dye in the course of thermal diffusion printing, the resulting prints being distinguished by excellent image quality such as sharpness, image stability and color density. The coatings themselves also have little or no tendency to stick.

• a) Polyester,
• b) Polyether,
• c) Acrylat-Copolymerisat, oder
• d) aus einem oder mehreren der Monomere Vinylacetat, Vinylbutyral, Maleinsäure, Maleinsäuredi-n-butylester, Crotonsäure, Vinyllaurat, Acrylnitril und Ethylen aufgebauten Copolymerisat

durch Vernetzung mit einem Polyisocyanat gebildet ist und mindestens 4 Gew.-% Urethangruppne (-O-CO-NH-) aufweist.The present invention relates to a dye acceptor element for the thermal sublimation printing process with a dye acceptor layer which consists essentially of a polyurethane formed by crosslinking, characterized in that the polyurethane consists of a hydroxyl group-containing

• a) polyester,
• b) polyether,
• c) acrylate copolymer, or
• d) copolymer composed of one or more of the monomers vinyl acetate, vinyl butyral, maleic acid, maleic acid di-n-butyl ester, crotonic acid, vinyl laurate, acrylonitrile and ethylene

is formed by crosslinking with a polyisocyanate and has at least 4% by weight of urethane groups (-O-CO-NH-).

Urethane groups generally arise in the production of polyurethanes by reaction between hydroxyl groups and isocyanate groups. Accordingly, the polyurethanes according to the invention are formed by reacting polymers which contain at least 2 hydroxyl groups (polymeric polyols) with compounds which contain at least 2 isocyanate groups (polyisocyanates). At least one of the two reaction components (polymeric polyol, polyisocyanate) is completely or (in the case of mixtures) partially tri- or higher-functional, which means that in the reaction mixture at least one polyol with 3 or more hydroxyl groups and / or a polyisocyanate with 3 or more Isocyanate groups must be present.

The polymeric polyols can be, for example, polyesters, polyethers or polyvinyl compounds, or else polymers or prepolymers which already contain urethane groups.

_n) von 250 bis 3.000, beispielsweise auf Basis von zweiwertigen und gegebenenfalls zusätzlich drei- oder mehrwertigen Alkoholen mit mehrwertigen, vorzugsweise zweiwertigen, Carbonsäuren (Polycarbonsäuren). Anstelle der freien Polycarbonsäuren können auch die entsprechenden Polycarbonsäureanhydride oder entsprechende Polycarbonsäureester von niedrigen Alkoholen oder deren Gemische zur Herstellung der Polyester verwendet werden. Die Polycarbonsäuren können aliphatischer, cycloaliphatischer, aromatischer und/oder heterocyclischer Natur sein und gegebenenfalls, z.B. durch Halogenatome, substituiert und/oder ungesättigt sein, Als Beispiele hierfür seien genannt: Bernsteinsäure, Adipinsäure, Azelainsäure, Sebacinsäure, Phthalsäure, Isophthalsäure, Trimellitsäure, Phthalsäureanhydrid, Tetrahydrophthalsäureanhydrid, Hexahydrophthalsäureanhydrid, Endomethylentetrahydrophthalsäureanhydrid, Glutarsäureanhydrid, Maleinsäure, Maleinsäureanhydrid, Fumarsäure, Terephthalsäuredimethylester und Terephthalsäure-bis-glykolester. Als mehrwertige Alkohole kommen z.B. Ethylenglykol, Propylenglykol-(1,2) und -(1,3), Butylenglykol-(1,4) und -(2,3), Hexandiol-(1,6), Octandiol-(1,8), Neopentylglykol, Cyclohexandimethanol (1,4-Bishydroxymethylcyclohexan), 2-Methyl-1,3-propandiol, Glycerin, Trimethylolpropan, Hexantriol-(1,2,6), Butantriol-(1,2,4), Trimethylolethan, Pentaerythrit, Chinit, Mannit und Sorbit, Methylglykosid, ferner Diethylenglykol, Triethylenglykol, Tetraethylenglykol, Polyethylenglykole, Dipropylenglykol, Polypropylenglykole, Dibutylenglykol und Polybutylenglykole in Frage. Auch Polyester aus Lactonen, z.B. ε-Caprolacton oder Hydroxycarbonsäuren, z.B. ω-Hydroxycapronsäure, sind einsetzbar. Weitere geeignete Polyester sind z.B. in Karsten "Lackrohstoff-Tabellen", 8. Auflage, 1987, beschrieben.Polyhydroxy polyesters with an average molecular weight ( $\overline{\text{M}}$

_n ) from 250 to 3,000, for example based on dihydric and optionally additionally trihydric or polyhydric alcohols with polyhydric, preferably dihydric, carboxylic acids (polycarboxylic acids). Instead of Free polycarboxylic acids, the corresponding polycarboxylic anhydrides or corresponding polycarboxylic acid esters of lower alcohols or mixtures thereof can also be used to produce the polyesters. The polycarboxylic acids can be aliphatic, cycloaliphatic, aromatic and / or heterocyclic in nature and optionally substituted, for example by halogen atoms, and / or unsaturated. Examples include: succinic acid, adipic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, trimellitic acid, phthalic anhydride Tetrahydrophthalic anhydride, hexahydrophthalic anhydride, endomethylene tetrahydrophthalic anhydride, glutaric anhydride, maleic acid, maleic anhydride, fumaric acid, dimethyl terephthalate and bis-glycol terephthalate. Polyhydric alcohols include, for example, ethylene glycol, propylene glycol (1,2) and - (1,3), butylene glycol (1,4) and - (2,3), hexanediol (1,6), octanediol (1, 8), neopentyl glycol, cyclohexanedimethanol (1,4-bishydroxymethylcyclohexane), 2-methyl-1,3-propanediol, glycerol, trimethylolpropane, hexanetriol (1,2,6), butanetriol (1,2,4), trimethylolethane, Pentaerythritol, quinite, mannitol and sorbitol, methyl glycoside, also diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycols, dipropylene glycol, polypropylene glycols, dibutylene glycol and polybutylene glycol in question. Polyesters made from lactones, for example ε-caprolactone or hydroxycarboxylic acids, for example ω-hydroxycaproic acid, can also be used. Other suitable polyesters are described, for example, in Karsten "Lackrohstoff-tables", 8th edition, 1987.

_n) von 1.000 bis 150.000. Dies sind bevorzugt:

• 1. Polyacrylate mit einem Hydroxylgruppengehalt von 1 bis 10 Gew.-%. Diese Verbindungen werden in an sich bekannter Weise durch Copolymerisation von olefinisch ungesättigten Monomeren unter Mitverwendung von Hydroxylgruppen aufweisenden, olefinisch ungesättigten Monomeren hergestellt. Geeignete Monomere sind beispielsweise Acrylsäure- und/oder Methacrylsäurealkylester mit 1 bis 6 Kohlenstoffatomen im Alkylrest wie beispielsweise Methylacrylat, Methylmethacrylat, Ethylacrylat, Ethylmethacrylat, n-Butylacrylat oder n-Hexylmethacrylat und/oder Styrol. Geeignete hydroxyfunktionelle Monomere sind beispielsweise Hydroxyalkylester der Acrylsäure oder Methacrylsäure mit 2 bis 6 Kohlenstoffatomen im Hydroxyalkylrest wie beispielsweise Hydroxyethyl-, 2-Hydroxypropyl-, 3-Hydroxypropyl-, 4-Hydroxybutyl- oder 6-Hydroxyhexylacrylat oder -methacrylat. Weitere geeignete Produkte sind z.B. in Karsten "Lackrohstoff-Tabellen", 8. Auflage, beschrieben.
• 2. Copolymerisate mit einem Hydroxylgruppengehalt von 1 bis 10 Gew.-%. Diese Verbindungen werden in an sich bekannter Weise durch Copolymerisation von olefinisch ungesättigten Monomeren unter Mitverwendung von zur späteren Freisetzung von Hydroxylgruppen geeigneten, olefinisch ungesättigten Monomeren hergestellt. Geeignete Monomere sind beispielsweise Vinylacetat, Vinylbutyral, Maleinsäure, Maleinsäuredi-n-butylester, Crotonsäure, Vinyllaurat, Acrylnitril und Ethylen. Die Hydroxylgruppen werden beispielsweise durch partielle Verseifung von Acetatgruppen oder durch Copolymerisation mit Hydroxylgruppen aufweisenden Vinylverbindungen wie z,B, unter 1. aufgeführt, erhalten, Als Beispiel für geeignete Hydroxylgruppen aufweisende Copolymere sei Polyvinylbutyral angeführt.

Preferred hydroxyl-containing polyvinyl compounds are those with an average molecular weight ( $\overline{\text{M}}$

_n ) from 1,000 to 150,000. These are preferred:

• 1. Polyacrylates with a hydroxyl group content of 1 to 10 wt .-%. These compounds are prepared in a manner known per se by copolymerization of olefinically unsaturated monomers with the use of hydroxyl-containing olefinically unsaturated monomers. Suitable monomers are, for example, acrylic acid and / or methacrylic acid alkyl esters with 1 to 6 carbon atoms in the alkyl radical, such as, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate or n-hexyl methacrylate and / or styrene. Suitable hydroxy-functional monomers are, for example, hydroxyalkyl esters of acrylic acid or methacrylic acid having 2 to 6 carbon atoms in the hydroxyalkyl radical, such as, for example, hydroxyethyl, 2-hydroxypropyl, 3-hydroxypropyl, 4-hydroxybutyl or 6-hydroxyhexyl acrylate or methacrylate. Other suitable products are described, for example, in Karsten "Lacquer Raw Material Tables", 8th edition.
• 2. Copolymers with a hydroxyl group content of 1 to 10 wt .-%. These compounds are obtained in a manner known per se by copolymerization of olefinically unsaturated monomers with the use of suitable for the later release of hydroxyl groups, olefinically unsaturated monomers. Suitable monomers are, for example, vinyl acetate, vinyl butyral, maleic acid, maleic acid di-n-butyl ester, crotonic acid, vinyl laurate, acrylonitrile and ethylene. The hydroxyl groups are obtained, for example, by partial saponification of acetate groups or by copolymerization with vinyl compounds having hydroxyl groups, such as, for example, listed under 1. Polyvinyl butyral may be mentioned as an example of suitable copolymers having hydroxyl groups.

Such and other products of this type are commercially available and are described, for example, in Karsten "Lackrohstoff tables, 8th edition.

• (i) einfache organische Polyisocyanate des Molekulargewichtsbereichs 168 bis 300 wie z,B, 1,6-Diisocyanatohexan, 1-Isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexan, 2,4- und/oder 2,6-Diisocyanatotoluol, 4,4'- und/oder 2,4'-Diisocyanatodiphenylmethan oder 4,4'-Diisocyanato-dicyclohexylmethan.
  Diese einfachen Diisocyanate werden allerdings weniger bevorzugt verwendet.
• (ii) Modifizierte "Lackpolyisocyanate" mit einem mittleren Molekulargewicht von bis 1.000, d.h., die an sich bekannten Urethan-, Biuret-, Isocyanurat-, Uretdion-, Uretonimin- oder Oxadiazintriongruppen aufweisenden, modifizierten Polyisocyanate auf Basis der unter (i) genannten einfachen Diisocyanate, wie beispielsweise das Tris-(6-isocyanatohexyl)-biuret oder dessen Gemische mit seinen höheren Homologen oder das Tris-(6-isocyanatohexyl)-isocyanurat oder seine Gemische mit seinen höheren Homologen und gegebenenfalls mit dem Bis-(6-isocyanatohexyl)-uretdion oder Bis-(6-isocyanatohexyl)-oxadiazintrion.

Polyisocyanate compounds which can be used as starting materials for the production of the color acceptor layer in the color acceptor element according to the invention are, for example:

• (i) simple organic polyisocyanates of the molecular weight range 168 to 300 such as, for example, 1,6-diisocyanatohexane, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethyl-cyclohexane, 2,4- and / or 2,6 -Diisocyanatotoluene, 4,4'- and / or 2,4'-diisocyanatodiphenylmethane or 4,4'-diisocyanato-dicyclohexylmethane.
  However, these simple diisocyanates are used less preferably.
• (ii) Modified "paint polyisocyanates" with an average molecular weight of up to 1,000, ie the known modified urethane, biuret, isocyanurate, uretdione, uretonimine or oxadiazinetrione groups, based on the simple polyisocyanates mentioned under (i) Diisocyanates, such as, for example, the tris (6-isocyanatohexyl) biuret or its mixtures with its higher homologues or the tris (6-isocyanatohexyl) isocyanurate or its mixtures with its higher homologues and optionally with the bis (6-isocyanatohexyl) uretdione or bis (6-isocyanatohexyl) oxadiazinetrione.

Starting polyisocyanates with aliphatically bound isocyanate groups are preferably used in the process according to the invention. Aliphatic lacquer polyisocyanates of the type exemplified under (ii) are particularly preferred starting materials, optionally in a mixture with aromatic polyisocyanates.

In principle, it is also possible to use polyisocyanate compounds which still have built-in carboxylate groups. This would be possible, for example, by reacting, for example, hydroxycarboxylic acids such as dimethylolpropionic acid with the corresponding amounts of isocyanate.

Polyols and polyisocyanates together form a reactive mixture for producing the essential constituent or main constituent of the color acceptor layer according to the invention. The polyols and polyisocyanates are selected and used in such a mixing ratio that, when cured, a crosslinked, insoluble polyurethane is formed which contains at least 4% by weight, preferably 5 to 20% by weight and even more preferably 6 to Contains 12 wt .-%, urethane groups (-O-CO-NH-). A substantial proportion of these urethane groups is newly formed during the reaction of the polyols with the polyisocyanates, but a further proportion of the urethane groups may already have been contained in the polyol component and / or the polyisocyanate component. The ratio of isocyanate groups to hydroxyl groups before crosslinking is between 0.6: 1 and 1.5: 1 and preferably about 1: 1.

• a) Polymere, die Esterbindungen enthalten: Polyester, Polyacrylester, Polycarbonate, Polyvinylacetat, Polyvinylpropionat, Styrol-Acrylate, Methylstyrol-Acrylate usw.
• b) Polymere, die Urethanbindungen enthalten: Polyurethane, Polyesterurethane usw.
• c) Polymere, die Amidbindungen enthalten: Polyamide, Polyesteramide usw.
• d) Polymere, die Harnstoffbindungen enthalten: Polyharnstoffe usw.
• e) Polymere, die andere hochpolare Bindungen enthalten, wie z.B. Polystyrole, Polyvinylalkohol, Polyvinylchlorid, Polyacrylnitril, Polyether, Polysulfone, Polyetherketone, Polyhydantoin, Polyimide, Styrol-MSA-Copolymere, Cellulosederivate usw.

The starting products for the production of the polyurethanes according to the invention can also be used in a mixture with other known, preferably non-reactive resins for color acceptor layers; For example, the following polymers a) to e) can be used alone or as mixtures of one or more in combination with the polyols and polyisocyanates:

• a) Polymers containing ester bonds: polyesters, polyacrylic esters, polycarbonates, polyvinyl acetate, polyvinyl propionate, styrene-acrylates, methylstyrene-acrylates, etc.
• b) Polymers containing urethane bonds: polyurethanes, polyester urethanes, etc.
• c) Polymers containing amide bonds: polyamides, polyester amides, etc.
• d) polymers containing urea bonds: polyureas, etc.
• e) Polymers containing other highly polar bonds, such as polystyrenes, polyvinyl alcohol, polyvinyl chloride, polyacrylonitrile, polyethers, polysulfones, polyether ketones, polyhydantoin, polyimides, styrene-MSA copolymers, cellulose derivatives, etc.

Examples of such resins are e.g. described in EP-A-0 227 094, EP-A-0 228 066, EP-A-0 133 011, EP-A-0 133 012 or EP-A-0 144 247.

In the cases in which the starting products for the production of the polyurethanes according to the invention are used in combination with other resins, the proportion of the other resins is between 0 and 50% by weight of the total mixture.

High-boiling solvents or plasticizers can also be added to the color acceptor layer. For example, you can ensure better solubility of the transferred dyes. Usable representatives of these compounds are listed, for example, in JP 62/174 754, JP 62/245 253, JP 61/209 444, JP 61/200 538, JP 62/136 646, JP 62/30 274.

The color acceptor layer can e.g. pigments or mixtures of several pigments, such as e.g. Titanium dioxide, zinc oxide, kaolin, clay, calcium carbonate or Aerosil can be added.

To further increase the light stability of the transferred image, one or different types of additives, such as e.g. UV absorbers, light stabilizers or antioxidants can be added.

The color acceptor layers of the present invention can contain a lubricant to improve the sliding properties, primarily between the donor and acceptor elements. For example, solid waxes such as polyethylene wax, amidic waxes or teflon powder can be used. However, optionally fluorine-containing surfactants, paraffin, silicone or fluorine-containing oils or silicone-containing copolymers such as polysiloxane polyether copolymers can also be used for this purpose.

The lubricant mentioned can also be used as a separate coating, e.g. be applied as a dispersion or as a solution in a suitable solvent as a "top coat". The thickness of such a layer is then preferably 0.01 to 5 μm, particularly preferably between 0.05 and 2 μm.

A particular advantage of the color acceptor element according to the invention can be seen in the fact that the polyurethane used in the color acceptor layer due to the comparative high content of urethane groups and the resulting high degree of crosslinking has an extremely low tendency to stick. Therefore, the use of a lubricant, be it in admixed form or as a separate coating, can also be dispensed with without the layers adhering during the ink transfer. This is particularly advantageous because a reduced color density, sharpness and stability of the transferred color image are often observed when using a lubricant.

Various materials can be used as a support for the color acceptor layers. It is possible to use transparent films such as e.g. Use polyethylene terephthalate, polycarbonate, polyether sulfone, polyolefin, polyvinyl chloride, polystyrene, cellulose or polyvinyl alcohol copolymer films. Of course, there are also reflective documents such as the most varied types of paper, e.g. Polyolefin-coated paper or pigmented papers, for use. Also laminates from the above Materials are applicable. Typical combinations are laminates of cellulose paper and synthetic paper, cellulose paper and polymer films or polymer films and synthetic paper or other combinations.

The carriers ensure the necessary mechanical stability of the color acceptor element. If the color acceptor layer has sufficient mechanical stability can be dispensed with an additional carrier.

The color acceptor layers of the present invention preferably have a total layer thickness in the range from 0.3 to 50 μm, particularly preferably from 0.5 to 10 μm, if a carrier of the type described above is used or if this is dispensed with, in the range from 3 to 120 µm. The color acceptor layer can consist of a single layer, but two or more layers can also be applied to the support. When using transparent supports, a double-sided coating can be applied to increase the color intensity, e.g. described in European patent application 90 200 930.7.

The ink receiving element of the present invention can also contain various intermediate layers between the base and the actual ink acceptor layer. Depending on the specific properties of the material used, the intermediate layer can act as a resilient element (elastic layer), as a barrier layer for the transferred dye or as an adhesive layer, depending on the specific application. Examples of suitable materials are urethane, acrylate or olefin resins, but also butadiene rubbers or epoxies. The thickness of this intermediate layer is usually between about 1 to 2 and 20 microns. Diffusion barrier layers have the task of diffusing the transferred dyes to prevent in the carrier. Materials that fulfill this task can be soluble in water or in organic solvents or in mixtures. Suitable materials are, for example, gelatin, polyacrylic acid, maleic anhydride copolymers, polyvinyl alcohol or cellulose acetate.

The optional additional layers such as elastic layer, diffusion barrier layer, adhesive layer etc. as well as the actual color acceptor layer can e.g. Contain silicate, clay, aluminum silicate, calcium carbonate, calcium sulfate, barium sulfate, titanium dioxide, aluminum oxide powder.

The color acceptor elements of the present invention can also be antistatically treated on the front or back in the usual manner. They can be provided with markings, preferably on the back of the carrier, in order to enable precise positioning during the printing process.

The color acceptor element according to the invention can be combined with the color donor elements customary in the field of thermal sublimation printing.

The color images obtained in a thermal sublimation printer are characterized by high resolution, high color densities, high brilliance and good long-term stability.

The mixture is usually processed from solution to produce the color acceptor layers according to the invention. Suitable solvents are, for example Methyl ethyl ketone, toluene, xylene, butyl acetate, methylene chloride, chlorobenzene, tetrahydrofuran or dioxane. The solution can be applied to the support by casting or knife coating or by printing. The coating is then annealed to remove the solvent and to cause crosslinking of the polyols and polyisocyanates to form the crosslinked polyurethane. The conditions of the tempering depend on the circumstances of the individual case, for example the type of substrate and the solvent used, the layer thickness and the reactivity of the reactive components used.

Examples

The formulations listed in Table 1 were used to produce color acceptor layers. The stoichiometry was chosen so that there were equal equivalents of isocyanate and hydroxyl groups. The respective delivery form of the starting compounds was diluted with methyl ethyl ketone so that 25% solutions including 0.25% tin-II-octoate (Desmorapid® SO) could be poured onto a paper in a wet film thickness of 25 µm using a doctor knife, which was coated on both sides with polyethylene and on one side of which a gelatin layer had additionally been applied over the polyethylene. The coating was applied to this side. The coatings were dried in a forced-air drying cabinet at 70 ° C. for 30 minutes. These samples are designated A in the table. A 0.5% solution in ethanol from Tego Glide 410 (Goldschmidt) with a wet film thickness of 24 μm was then applied to the samples designated B in the table and at 70 in a circulating air dryer ° C dried. Test images were generated on the dye-receiving elements obtained using a Mitsubishi CP-100 E video printer using the Mitsubishi dye cassette CK-100 S.

The color acceptor layers, which are built up from the crosslinked systems according to the invention, are distinguished by increased color densities and greatly reduced tendency of the prints to stick. In addition, they have high sharpness after tempering.

• a) Polyisocyanate (Spalte "P-iso")
  • 1. Desmodur® 3390
    aliphatisches Polyisocyanat
    NCO-Gehalt: ca, 19,4 %
  • 2. Desmodur® 2550
    niedrig-viskoses, aliphatisches Polyisocyanat
    NCO-Gehalt: ca, 22 %
  • 3. Desmodur® 4370
    polyfunktionelles, aliphatisches Polyisocyanat
    NCO-Gehalt: ca. 11,5 %
  • 4. Desmodur® W
    4,4'-Diisocyanato-dicyclohexylmethan
  • 5. Desmodur® H
    Hexamethylendiisocyanat
  • 6. Desmodur® HL
    aromatisch-aliphatisches Polyisocyanat
    NCO-Gehalt: ca. 10,5 %
  
  Desmodur® ist ein eingetragenes Warenzeichen der Bayer AG, Leverkusen.
• b) Polyole (Spalte "P-ol")
  • 1. Desmophen® A 265
    hydroxylgruppenhaltiges Polyacrylat
    OH-Gehalt: ca. 2,2 %
  • 2. Desmophen® 680
    hydroxylgruppenhaltiger Polyester, enthält verzweigte, schwach ungesättigte C₁₈-Fettsäuren
    OH-Gehalt: ca, 2,0 %
  • 3. Crelan® U 502
    hydroxylgruppenhaltiger, ölfreier, gesättigter Polyester auf Terephthalatsäurebasis
    OH-Gehalt: ca. 1,5 %
  • 4. Desmophen® A 160
    hydroxylgruppenhaltiges Polyacrylat
    OH-Gehalt: ca. 1,6 %
  • 5. Desmophen® 670
    schwach verzweigter, hydroxylgruppenhaltiger Polyester
    OH-Gehalt: ca. 4,3 %
  • 6. Desmophen® 900 U
    hydroxylgruppenhaltiger, verzweigter Polyether
    OH-Gehalt: ca, 8,8 %
  • 7. Desmophen® A 365
    hydroxylgruppenhaltiges Polyacrylat
    OH-Gehalt: ca, 2,8 %
  Desmophen® und Crelan® sind eingetragene Warenzeichen der Bayer AG, Leverkusen.

The following prepolymers were used in the samples described in the table:

• a) polyisocyanates (column "P-iso")
  • 1. Desmodur® 3390
    aliphatic polyisocyanate
    NCO content: approx. 19.4%
  • 2. Desmodur® 2550
    low-viscosity, aliphatic polyisocyanate
    NCO content: approx. 22%
  • 3. Desmodur® 4370
    polyfunctional, aliphatic polyisocyanate
    NCO content: approx.11.5%
  • 4. Desmodur® W
    4,4'-diisocyanatodicyclohexylmethane
  • 5. Desmodur® H
    Hexamethylene diisocyanate
  • 6. Desmodur® HL
    aromatic-aliphatic polyisocyanate
    NCO content: approx.10.5%
  
  Desmodur® is a registered trademark of Bayer AG, Leverkusen.
• b) polyols (column "P-ol")
  • 1. Desmophen® A 265
    polyacrylate containing hydroxyl groups
    OH content: approx.2.2%
  • 2. Desmophen® 680
    hydroxyl-containing polyester, contains branched, weakly unsaturated C₁₈ fatty acids
    OH content: approx. 2.0%
  • 3. Crelan® U 502
    Hydroxyl-containing, oil-free, saturated polyester based on terephthalic acid
    OH content: approx.1.5%
  • 4. Desmophen® A 160
    polyacrylate containing hydroxyl groups
    OH content: approx.1.6%
  • 5. Desmophen® 670
    slightly branched, hydroxyl-containing polyester
    OH content: approx.4.3%
  • 6. Desmophen® 900 U
    branched polyether containing hydroxyl groups
    OH content: approx.8.8%
  • 7. Desmophen® A 365
    polyacrylate containing hydroxyl groups
    OH content: approx. 2.8%
  Desmophen® and Crelan® are registered trademarks of Bayer AG, Leverkusen.

The examples labeled "A" contain no lubricant.

The examples labeled "B" also contain a separate layer of lubricant.

Correspondingly, further color acceptor elements were produced in accordance with the present invention. The formulations used and the results obtained with them are given in Table 2.

Further samples 24 and 25 were produced by applying the compositions of samples 18 and 23 to a transparent PET film with a thickness of 175 μm (instead of the polyethylene-coated paper). The same results as given in table 2 were achieved.

Claims (7)

Ink acceptor element for the thermal sublimation printing process with a dye acceptor layer which consists essentially of a polyurethane formed by crosslinking, characterized in that the polyurethane consists of a hydroxyl group-containing a) polyester, b) polyether, c) acrylate copolymer, or d) copolymer composed of one or more of the monomers vinyl acetate, vinyl butyral, maleic acid, maleic acid di-n-butyl ester, crotonic acid, vinyl laurate, acrylonitrile and ethylene is formed by crosslinking with a polyisocyanate and has at least 4% by weight of urethane groups (-O-CO-NH-). Color acceptor element according to Claim 1, characterized in that the polyurethane has 5 to 20% by weight of urethane groups. Color acceptor element according to one of claims 1 and 2, characterized in that the polyurethane by crosslinking from a urethane group containing Polyol component is formed with a polyisocyanate component optionally containing urethane groups. Color acceptor element according to claim 3, characterized in that at least one polyol of the polyol component contains 3 or more hydroxyl groups and / or at least one polyisocyanate of the polyisocyanate component contains 3 or more isocyanate groups. Color acceptor element according to claim 3, characterized in that the polyol component consists of one or more hydroxyl-containing polyesters, one or more hydroxyl-containing polyethers and / or one or more hydroxyl-containing polyvinyl compounds. Color acceptor element according to claim 3, characterized in that the polyisocyanate component consists of one or more, optionally containing urethane, biuret, isocyanurate, uretdione, uretonimine or oxadiazinetrione groups. Color acceptor element according to one of claims 1 to 6, characterized in that it contains no lubricant.