EP0498245A1 - Dye receiving sheet for the thermosublimation printing process - Google Patents

Abstract

A dye acceptor element for the thermal sublimation printing process with a support and a dye acceptor layer thereon, consisting essentially of polycarbonate, the polycarbonate containing 30 to 95% by weight of aromatic carbonate structural units of the formula I [-O-diphen-O-CO-] (I) wherein diphen stands for the remainder of a diphenol with 6 to 30, preferably with 12 to 24, carbon atoms and contains 70 to 5% by weight of aliphatic polyether carbonate structural units of the formula II, [-O-polyether-O-CO -] (II) in which polyether stands for the remainder of an aliphatic polyether diol with a molecular weight Mn of 600 to 20,000, is characterized by high color density and low tendency to stick.

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 dye capable of sublimation is brought into contact with a dye (material) acceptor layer and heated imagewise to transfer the dye.

The thermal head is controlled and the dye is transferred from the donor material to the acceptor 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 acceptor layer.

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

• 1. Synthetische Harze mit Esterverbindungen, wie Polyester, Polyacrylate, Polyvinylacetat, Styrol-Acrylat-Harze und Vinyltoluol-Acrylat-Harze
• 2. Polyurethane
• 3. Polyamide
• 4. Harnstoff-Harze
• 5. Synthetische Harze mit anderen hochpolaren Bindungen, wie Polycaprolactam, Styrol-Harze, Polyvinylchlorid, Vinylchlorid-Vinylacetat-Copolymere und Polyacrylnitril.

The following examples of suitable materials for the acceptor layer are mentioned in EP-A-0 234 563:

• 1. Synthetic resins with ester compounds such as polyesters, polyacrylates, polyvinyl acetate, styrene-acrylate resins and vinyltoluene-acrylate resins
• 2. Polyurethanes
• 3. Polyamides
• 4. urea resins
• 5. Synthetic resins with other highly polar bonds, such as polycaprolactam, styrene resins, polyvinyl chloride, vinyl chloride-vinyl acetate copolymers and polyacrylonitrile.

US-A-4 705 522 specifies polycarbonate, polyurethane, polyester, polyvinyl chloride, poly (styrene-co-acrylonitrile), polycaprolactone and mixtures thereof for the color acceptor layer.

EP-A-0 228 066 describes a color acceptor layer with improved light stability, which contains a mixture of polycaprolactone or a linear aliphatic polyester with poly (styrene-co-acrylonitrile) and / or bisphenol-A polycarbonate.

EP-A-0 227 094 describes a color acceptor element based on bisphenol A polycarbonate, which can be processed into layers with a particularly low surface roughness at a molecular weight of the polycarbonate of greater than 25,000. From US-A-4 927 803 a polycarbonate receiving layer is known in which the polycarbonate is built up from bisphenol-A and non-aromatic diols.

The products described there do not contain any polyether segments with higher molecular weights. In addition, they are not commercially available and can only be obtained by a manufacturing process that is restricted to the laboratory scale. A technical use is therefore excluded.

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 do large 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. The object is achieved by using a special polymer in the color acceptor element.

A color acceptor element for the thermal sublimation printing process has now been found, in which a polyether carbonate (PEC) is used in the color acceptor layer, optionally in a mixture with other suitable partners.

The invention relates to a dye acceptor element for the thermal sublimation printing process with a support and a dye acceptor layer thereon, consisting essentially of polycarbonate, characterized in that the polycarbonate contains 30 to 95% by weight of aromatic carbonate structural units of the formula I.



[-O-diphen-OC) -] (I)



wherein diphen stands for the remainder of a diphenol with 6 to 30, preferably with 12 to 24, carbon atoms,
and contains 70 to 5% by weight of aliphatic polyether carbonate structural units of the formula II,



[-O-polyether-O-CO-] (II)



wherein polyether represents the remainder of an aliphatic polyether diol with a molecular weight Mn of 600 to 20,000, preferably of 4,000 to 10,000,
where up to about 8% by weight, preferably up to about 4% by weight, of the diphenol portion can be replaced by C₂-C₁₅-alkylene diols and / or C₅- or C₆-cycloalkylene diols,
and optionally up to about 20 mol% of the carbonate groups -O-CO-O- can be replaced by aromatic and / or (cyclo) -aliphatic dicarboxylate groups.

_w (Gewichtsmittel) von 20.000 bis 350.000, vorzugsweise 100.000 bis 250.000 (ermittelt nach der Lichtstreumethode mit dem Streulichtphotometer).The polymers used according to the invention in the color acceptor layer are segmented, aliphatic-aromatic polyether copolycarbonates with a molecular weight $\overline{\text{M}}$

_w (weight average) from 20,000 to 350,000, preferably 100,000 to 250,000 (determined according to the light scattering method with the scattered light photometer).

Optionally, a part, up to about 20 mol%, preferably up to about 10 mol% of the carbonate groups -O-CO-O- by terephthalate and / or isophthalate groups and / or a part, up to about 10 mol%, preferably up to about 5 mol% of the carbonate groups can be replaced by C₂-C₁₅ alkylene dicarboxylate groups and / or C₅ or C₆ cycloalkylene dicarboxylate groups.

The segmented, aliphatic-aromatic polyether copolycarbonates are known (see, for example, DE-A-2 251 066, US-A-4 160 791, US-A-4 075 108 and US-A-4 069 151).

For example, they can be made from diphenols using the phase interface method



HO-phen-OH (III),



Polyether diphenol carbonates HO-phen-O-CO-O-polyether-O-CO-O-phen-OH and phosgene can be prepared in a known manner (see. DE-A-34 08 804).

Here, the corresponding part of the diphenols HO-phen-OH can be replaced by the C₂-C₁₅ alkylene diols or the C₅- or C₆-cycloalkylene diols and also used in the form of their bischlorocarbonic acid esters; a corresponding part of the phosgene can also be replaced by terephthalic acid dichloride, isophthalic acid dichloride and / or the C₂-C₁₅ alkanedicarboxylic acid dichlorides or C bzw.- or C₆-cycloalkanedicarboxylic acid dichlorides.

To regulate the molecular weights of the segmented aliphatic-aromatic polyether copolycarbonates, monophenols or aromatic monocarboxylic acid chlorides can be used in the usual amounts in a known manner.

The polyether copolycarbonates can be linear or branched in a known manner, for example by incorporating triphenols.

Diphenols (III) suitable according to the invention are, for example, bis (hydroxyphenyl) alkanes, bis (hydroxyphenyl) cycloalkanes and dicycloalkanes, dihydroxydiphenyls, bis (hydroxyphenyl) ethers, bis (hydroxyphenyl) sulfones, Bis (hydroxyphenyl) sulfides, bis (hydroxyphenyl) ketones, α, α-bis (hydroxyphenyl) diisopropylbenzenes and their alkylated compounds.

worin bedeuten

X

eine Einfachbindung, Methylen, Isopropyliden, Cyclohexyliden, Sauerstoff, Schwefel, Sulfon oder Carbonyl;

Y₁ bis Y₄

(gleich oder verschieden) Wasserstoff oder C₁-C₄-Alkyl, vorzugsweise H oder Methyl.

Preferred diphenols (III) correspond to formula IV

in what mean

X

a single bond, methylene, isopropylidene, cyclohexylidene, oxygen, sulfur, sulfone or carbonyl;

Y₁ to Y₄

(identical or different) hydrogen or C₁-C₄-alkyl, preferably H or methyl.

Examples of diphenols (III) are:
4,4'-dihydroxydiphenyl,
2,4'-dihydroxydiphenyl,
4,4'-dihydroxy-3,3 ', 5,5'-tetramethyldiphenyl,
4,4'-dihydroxy-3,3'-dimethyldiphenyl,
Bis (4-hydroxyphenyl) methane,
Bis (4-hydroxy-3,5-dimethylphenyl) methane,
Bis (4-hydroxyphenyl) ethane,
2,2-bis (4-hydroxyphenyl) propane ("bisphenol A"),
2,2-bis (4-hydroxy-3,5-dimethylphenyl) propane,
2,2-bis (4-hydroxy-3-methylphenyl) propane,
1,1-bis (4-hydroxyphenyl) cyclohexane,
1,1-bis (4-hydroxy-3,5-dimethylphenyl) cyclohexane,
Bis (4-hydroxyphenyl) oxide,
Bis (4-hydroxy-3,5-dimethylphenyl) oxide,
Bis (4-hydroxyphenyl) ketone,
Bis (4-hydroxy-3,5-dimethylphenyl) ketone,
Bis- (4-hydroxy-3,5-diethylphenyl) propane,
Bis (4-hydroxyphenyl) sulfone,
Bis (4-hydroxy-3,5-dimethylphenyl) sulfone,
Bis (4-hydroxyphenyl) sulfide and
Bis (4-hydroxy-3,5-dimethylphenyl) sulfide.

The following are particularly preferred:
2,2-bis (4-hydroxyphenyl) propane ("bisphenol A"),
2,2-bis (hydroxy-3,5-dimethylphenyl) propane.

Aliphatic polyether diols suitable for the production of the polyether diphenol carbonates are preferably polyethylene glycols, such as those from Union Cabide (Carbowax), British Petrol (Breox), Hoechst (Polyglycol) and Hüls (Polywachs) with molecular weights (number average molecular weights) of 600 to 20,000, are preferred 4,000 to 10,000. In addition to the polyethylene glycols mentioned, other hydroxyl-containing polyethers, e.g. Polyethylene oxide / propylene oxide mixed and block polyethers are used.

C₂-C₁₅ alkylene diols are, for example, ethylene glycol, 1,2-propanediol, 1,4-butanediol, 1,6-hexanediol, 1,8-octanediol, 1,12-dodecanediol and 1,2-dihydroxidodecane; a suitable one Cycloalkylene diol is, for example, 1,4-dihydroxycyclohexane; C₂-C₁₅ alkanedicarboxylic acid dichlorides are, for example, succinic acid dichloride, adipic acid dichloride, azelaic acid dichloride, sebacic acid dichloride and dodecanedicarboxylic acid dichloride; Suitable cycloalkanedicarboxylic acid dichlorides are, for example, hexahydroterephthaloyl chloride and hexahydro-isophthaloyl chloride.

Suitable phenolic chain terminators are all customary phenols, such as phenol itself, p-tert-butylphenol and p-di-tert-octylphenol, and monofunctional polyethers, and benzoic acid chloride and alkylbenzoic acid chloride as aromatic monocarboxylic acid chlorides.

Preferred ratios of aromatic carbonate structural units (I) to aliphatic polyether carbonate structural units (II) are 30% by weight to 55% by weight (I) to 70% by weight to 45% by weight (II), since here the water-spreading effect is also available without the addition of surfactants.

The polyether copolycarbonates to be used according to the invention have relative solution viscosities (measured on solutions of 0.5 g in 100 ml of methylene chloride at 25 ° C.) between 1.1 and 3.8, preferably between 1.5 and 3.8.

_n (Zahlenmittel) der Polyetherdiole werden ermittelt durch Gelpermeationschromatographie und Hydroxylzahl.The molecular weights $\overline{\text{M}}$

_n (number average) of the polyether diols are determined by gel permeation chromatography and hydroxyl number.

• 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. Polycaprolacton, Polystyrole, Polyvinylalkohol, Polyvinylchlorid, Polyacrylnitril, Polyether, Polysulfone, Polyetherketone, Polyhydantoin, Polyimide, Styrol-MSA-Copolymere, Cellulosederivate usw.

The polyether carbonates can also be used in mixtures with other known resins for color acceptor layers; For example, the following polymers a) to e) can be used alone or as mixtures of several in combination with the polyether carbonates as the dye-receiving material.

• 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 that contain other highly polar bonds, such as polycaprolactone, polystyrenes, polyvinyl alcohol, polyvinyl chloride, polyacrylonitrile, polyethers, polysulfones, polyether ketones, polyhydantoin, polyimides, styrene-MSA copolymers, cellulose derivatives, etc.

Examples of such resins are described, for example, 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 cases where the polyether carbonates are used in combination with other resins mentioned above as a color acceptor layer, 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. Useful representatives of these compounds are e.g. cited 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, various 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, but also, if appropriate, fluorine-containing surfactants, paraffin, silicone or fluorine-containing oils or copolymers containing silicone such as polysiloxane polyether copolymers.

The lubricant mentioned can also be applied as a separate coating, as a dispersion or, if appropriate, from 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.

Various materials can be used as carriers for the color acceptor layers. It is possible to use transparent films such as 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 such as Polyolefin coated paper or pigmented papers are used. Laminates made from the above materials can also be used. Typical combinations are laminates of cellulose paper and synthetic paper or 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, an additional support can be dispensed with.

The color acceptor layers of the present invention preferably have total layer thicknesses of 0.3 to 50 μm, particularly preferably 0.5 to 10 μm, if a carrier of the type described above is used or if this is dispensed with, 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 color acceptor element of the present invention may also include various intermediate layers between the backing and the dye-receiving 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 preventing the transferred dyes from diffusing into the support. Materials which fulfill this task can be soluble in water or in organic solvents or in mixtures, but preferably in water. 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 image acceptor element of the present invention can also be antistatically equipped on the front or back in the usual way. It can also be provided with markings, preferably on the back of the carrier, in order to achieve 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 polyether carbonate from Example 1 used to construct the color acceptor element according to the invention is sold commercially by Bayer AG under the name KU 3013. The other polyether carbonates can be produced on a larger scale in an analogous manner.

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 color acceptor layers containing polyether carbonate are usually produced from solution. Suitable solvents are, for example, methylene chloride, chlorobenzene, THF or dioxolane. The solution can be applied to the support by pouring or knife coating.

Examples 1. Polyether carbonates

According to the process described in DE-A-34 08 804, polyether carbonates corresponding to the parts by weight given in Table 1 are prepared from polyethylene oxide and bisphenol A and phosgene (excess). The procedure here is that bisphenol A, polyether and sodium hydroxide solution are initially introduced in a methylene chloride / water mixture and then phosgene is introduced with an excess of 150 mol%, based on bisphenol A. At the same time, so much sodium hydroxide solution is metered in that a pH of 14 is kept constant. Table 1 example Polyether MG 8,000 Polyether MG 20,000 BPA-PC 1 20th - 80 2nd - 20th 80 3rd 30th - 70

2. Color acceptor layers

The copolycondensates obtained in Examples 1 to 3 were used to build up color acceptor layers as follows:

5% solutions of the polyether carbonates from Examples 1 and 2 and 10% solutions of the product from Example 3 in methylene chloride were prepared. The solutions were cast with the aid of a doctor blade in a wet film thickness of 20 μm onto a paper which was coated on both sides with polyethylene and on the one side of which a gelatin layer had additionally been applied over the polyethylene. The polyether carbonate layer was applied to this side. The coatings were dried in a forced-air drying cabinet at 90 ° C. for 60 minutes. A 0.5% strength solution in ethanol from Tego Glide 410 (Goldschmidt) was then applied with a wet film thickness of 24 μm and dried in a forced-air drying cabinet at 70 ° C. 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 polyether carbonates according to the invention are distinguished by increased color densities and greatly reduced tendency to stick.

Table 2 lists color densities, which were determined using a Macbeth RD 919 densitometer for the pure yellow field of the test image, and the adhesive behavior.

Examples 1 to 3 show that the color acceptor layers built up from the modified polycarbonates have higher color layers and have better adhesive properties (less sticking).

Claims (1)

Color acceptor element for the thermal sublimation printing process with a support and a color acceptor layer thereon, consisting essentially of polycarbonate, characterized in that the polycarbonate contains 30 to 95% by weight of aromatic carbonate structural units of the formula I



[-O-diphen-O-CO-] (I)



wherein diphen stands for the remainder of a diphenol with 6 to 30, preferably with 12 to 24, carbon atoms,

and contains 70 to 5% by weight of aliphatic polyether carbonate structural units of the formula II,



[-O-polyether-O-CO-] (II)



wherein polyether represents the remainder of an aliphatic polyether diol with a molecular weight Mn of 600 to 20,000,

where up to about 8% by weight of the diphenol portion can be replaced by C₂-C₁₅ alkylene diols and / or C₅ or C₆ cycloalkylene diols,

and optionally up to about 20 mol% of the carbonate groups -O-CO-O- can be replaced by aromatic and / or (cyclo) -aliphatic dicarboxylate groups.