EP0499099A1 - Receiving element for a thermosublimation process - Google Patents

Abstract

A colour receiving element for the thermosublimation printing process having a support and a colour receiving layer which contains a graft copolymer comprising an unsaturated copolyester as the graft base and a vinyl copolymer as the graft, is distinguished by high colour density, high sharpness, good image stability and low adhesive tendency.

Description

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

There are a number of methods for printing out video or computer-stored images, of which thermal sublimation printing has proven to be superior in certain requirements due to its advantages over other methods. This recording method is based on the thermally induced transfer of a dye from a sheet or ribbon-shaped color donor material to a color acceptor layer and is described, for example, in "High Quality Image Recording by Sublimation Transfer Recording Material", Electronic Photography Association Documents, 27 (2), 1988 and there literature cited described in detail. A particular advantage of this method is the possibility to fine-tune the color intensity.

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 Esterbindungen, wie Polyester, Polyacrylate, Polyvinylacetat, Styrol-Acrylat-Harze und Vinyltoluol-Acrylat-Harze
• 2. Polyurethane
• 3. Polyamide
• 4. Harzstoff-Harze
• 5. Synthetische Harze mit anderen hochpolaren Bindungen, wie Polycaprolactam, 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 bonds, such as polyesters, polyacrylates, polyvinyl acetate, styrene-acrylate resins and vinyltoluene-acrylate resins
• 2. Polyurethanes
• 3. Polyamides
• 4. Resin resins
• 5. Synthetic resins with other highly polar bonds, such as polycaprolactam, 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.

European patent applications EP-A-0 261 505, EP-A-0 275 319, EP-A-0 289 161 and EP-A-0 368 318 describe color-acceptor layers made of copolyesters in detail. Furthermore, EP-A-0 368 320 discloses acceptor layers based on graft copolymers which contain polysiloxane segments, fluorocarbon segments or long-chain alkyl segments.

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

Another difficulty is the tendency of the known receiving materials to stick to the color donor material.

The invention is based on the object of providing a color acceptor element for the thermal sublimation printing process which does not have the disadvantages described above. The task is solved by using a special graft polymer in the acceptor element.

The invention relates to a color acceptor material for the thermal sublimation printing process with a support and a color acceptor layer, which is characterized in that is that the color acceptor layer contains a graft polymer of an unsaturated copolyester as the graft base and a vinyl copolymer as the graft pad.

The graft preferably contains polymerized units of vinyl aromatics and / or (meth) acrylic esters with 1-3 C atoms in the alcohol radical.

• a) 10 - 80 Gew.-% Vinylaromat und/oder (Meth)acrylsäureester mit 1-3 C-Atomen im Alkoholrest
  und
• b) 20 - 90 Gew.-% weiteren Vinylmonomeren.

The graft pad particularly preferably consists of a vinyl copolymer

• a) 10 - 80 wt .-% vinyl aromatic and / or (meth) acrylic acid ester with 1-3 carbon atoms in the alcohol residue
  and
• b) 20-90% by weight of other vinyl monomers.

• b1) 10 - 70 Gew.-% (Meth)acrylsäureester mit 4-18 C-Atomen im Alkoholrest
• b2) 5 - 40 Gew.-% (Meth)acrylnitril
• b3) 0 - 30 Gew.-% weiteren Vinylmonomeren.

In a very particularly preferred embodiment, component b of the graft pad consists of:

• b1) 10-70% by weight of (meth) acrylic acid ester with 4-18 C atoms in the alcohol residue
• b2) 5-40% by weight (meth) acrylonitrile
• b3) 0-30% by weight of other vinyl monomers.

The weight ratio of graft base to graft pad is generally 10: 1 to 1: 5, preferably 5: 1 to 1: 3.

The unsaturated copolyester of the graft base consists of condensed residues of diols, dicarboxylic acids and optionally additionally hydroxycarboxylic acids with the proviso that 0.2 to 30 mol% of the condensed residues contain polymerizable double bonds.

Both aliphatic and aromatic diols can be used. Examples of aliphatic diols are:
Ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, neopentyl glycol, 1,2-hexanediol, 1,6-hexanediol, 1,4-cyclohexanediol, cyclohexanedimethanol- (1st , 4), 2,2'-bis (4-hydroxy-cyclohexyl) propane. Diols with long alkyl chains, such as 1,8-octanediol, 1,2-octanediol, 1,2-decanediol, 1,2-dodecanediol, 1,12-dodecanediol, 1,16-hexadecanediol, 1,20- Eicosanediol, glycerol monostearate, glycerol monolaurate and pentaerythritol distearate.

Examples of aromatic diols are: bisphenol-A, ethoxylated bisphenol-A, propoxylated bisphenol-A and p-xylylene glycol.

Suitable diols with polymerizable double bonds are e.g. 2,3-dihydroxypropyl acrylate, 2,3-dihydroxypropyl methacrylate, pentaerythritol diacrylate, 9-octadecene-1,12-diol and glycerol monoleate.

The dicarboxylic acids can be aliphatic or aromatic. Suitable aromatic dicarboxylic acids are, for example Phthalic acid, terephthalic acid, isophthalic acid, sulfoisophthalic acid, naphthalene-dicarboxylic acids and 2,2-bis (p-carboxyphenyl) propane.

Examples of aliphatic dicarboxylic acids include the following: malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, decanedicarboxylic acid, dodecylmalonic acid, octadecylmalonic acid, dodecylsuccinic acid, tetradecylsuccinic acid, hexadecylsuccinic acid and octadecylsuccinic acid. So-called dimer fatty acids derived from long-chain unsaturated monocarboxylic acids are also very suitable, for example the products registered under CAS Reg. Nos 68783-41-5 and 68956-10-5.

Dicarboxylic acids with polymerizable double bonds which are suitable for the invention are, for example, maleic acid, fumaric acid, itaconic acid, octenylsuccinic acid, isooctenylsuccinic acid, dodecenylsuccinic acid and docosenylsuccinic acid. Maleic acid is preferred.

Suitable hydroxycarboxylic acids are, for example, 12-hydroxystearic acid, 12-hydroxy-9-octadecenoic acid and ricinoleic acid.

Preferably 5-45 mol% of the condensed residues contain one or more aromatic groups.

The polyesters used as the graft base for the present invention can be used in various ways known condensation processes can be synthesized. Polycondensation at a high temperature in the melt is particularly suitable. Interfacial condensation can also be used.

If appropriate, the starting compounds used are not the diols and dicarboxylic acids but rather corresponding derivatives, for example epoxides or acetates instead of the diols or esters instead of the dicarboxylic acids.

It may be expedient to add polymerization inhibitors such as 2,5-di-tert-butylphenol to the condensation reaction in order to prevent a crosslinking reaction.

The molecular weights of the polyesters are generally in the range from 1000 to 30,000.

A hydrophilizing group, e.g. a carboxylate, a sulfonate, an alcoholate or a polyethylene oxide group can be incorporated into the polyester to make it water-dispersible. This can be done, for example, by using sulfoterephthalic acid, sulfoisophthalic acid or sulfoorthophthalic acid.

Vinyl aromatics (component a) which are suitable according to the invention are styrene, α-methylstyrene, p-methylstyrene, m-methylstyrene, p-tert-butylstyrene, p-chlorostyrene, p-chloromethylstyrene, vinylnaphthalene and vinylnaphthalene. Styrene is preferred.

(Meth) acrylic acid esters are understood to mean methacrylic acid esters and acrylic acid esters. (Meth) acrylic acid esters with 1-3 C atoms in the alcohol part are methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, isopropyl acrylate and isopropyl methacrylate.

The (meth) acrylic acid esters with 4-18 C atoms (component b1) are derived from optionally substituted, aliphatic, cycloaliphatic, aromatic or mixed aromatic aliphatic alcohols. The aliphatic radicals can be straight-chain as well as branched and interrupted by oxygen.

Examples of suitable (meth) acrylic acid esters include: n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, n-hexyl acrylate, n-hexyl methacrylate, ethylhexyl acrylate, ethylhexyl methacrylate, n-octyl acrylate, n-octyl methacrylate, dedylactyl acrylate, stearyl acrylate, stearyl methacrylate, Cyclohexylactylat, cyclohexyl methacrylate, 4-tert-butylcyclohexyl methacrylate, benzyl acrylate, benzyl methacrylate, phenylethyl acrylate, phenylethyl methacrylate, phenylpropyl acrylate, phenylpropyl methacrylate, Phenyloctylacrylat, Phenylnonlyacrylat, Phenylnonylmethacrylat, 3-methoxybutyl methacrylate, butoxyethyl acrylate, furfuryl methacrylate and tetrahydrofurfuryl acrylate.

Mixtures of different esters can of course also be used. Mixtures containing ethyl hexyl acrylate, decyl methacrylate, dodecyl methacrylate or phenyl ethyl acrylate are particularly suitable.

Mixtures of different esters can of course also be used. Mixtures containing ethyl hexyl acrylate, decyl methacrylate, dodecyl methacrylate or phenyl ethyl acrylate are particularly suitable.

The term (meth) acrylonitrile (component b2) means both methacrylonitrile and acrylonitrile.

Other suitable monomers (component b3) are vinylidene chloride, vinyl chloride, vinyl acetate, vinyl propionate, vinyl laurate and vinyl adipate. For good dispersibility in water, hydrophilic monomers can be used, for example, sulfoethyl methacrylate, acrylamidomethylsulfonic acid, (meth) acrylic acid, hydroxyethyl (meth) acrylate and monomers containing ethylene oxide, such as tetraethylene glycol mono (meth) acrylate.

The implementation of the grafting reaction is described in detail in the literature, for example in Houben-Weyl, Methods of Organic Chemistry, Volume E20 / Part 1, p. 626 ff. The initiation takes place with radical formers, preferably peroxides.

The reaction can be carried out in a homogeneous phase as a bulk or solution polymerization or in a heterogeneous hare as an emulsion polymerization. An emulsion polymerization process with sodium alkyl sulfonate as an emulsifier and potassium peroxydisulfate as an initiator is particularly suitable for the preparation of the graft polymers according to the invention.

Suitable substrates for the acceptor layer according to the invention are both papers, in particular synthetic papers and polymer-coated papers, as well as films based on e.g. Polyester, polyamide, polyvinyl chloride or polycarbonate.

Of course, in addition to the acceptor layer according to the invention, the receiving element can contain further layers known for this purpose. It can be beneficial to apply a non-stick layer over the acceptor layer. As a non-stick layer e.g. low and high molecular weight polysiloxanes and polysiloxane-polyether block copolymers are well suited. In order to improve the adhesion of the acceptor layer to the carrier material, an intermediate layer made of gelatin, for example, can be applied.

The graft polymers can be processed from solution or, preferably, aqueous dispersion. Suitable solvents are, for example, acetone, methyl ethyl ketone, tetrahydrofuran, dioxane, ethyl acetate, dichloromethane and dimethylformamide. The solution or dispersion can be applied to the support by casting or knife coating.

The color acceptor material according to the invention can be combined with the color donor elements customary in the thermal sublimation field. There is no tendency to bond donor and acceptor material. The color images obtained are characterized by high resolution, high color saturation, high brilliance and good long-term stability.

example 1 Production of an unsaturated polyester

A mixture of 0.400 mol dimethyl terephthalate, 0.400 mol dimethyl isophthalate, 0.150 mol dimethyl 5-sulfoisophthalate, 0.05 mol maleic acid and 1 mol 1,10-decanediol were mixed together with 0.0002 mol zinc acetate and 0.0001 mol antimony-III-oxide melted and stirred in a reactor under nitrogen atmosphere at 200 ° C.

The esterification started quickly and methanol was first distilled off under normal pressure. The reaction product was then further condensed under reduced pressure at 200 ° C. to 250 ° C. until the expected degree of polymerization was reached (approx. 60 to 120 min). The yield was 100%.

Example 2-9

Further unsaturated polyesters were synthesized in accordance with the procedure given in Example 1. The components on which the starting components are based are listed in Table 1.

The numerical values in the table indicate the proportion of the diol or dicarboxylic acid residues in mol%, based on the total diol or dicarboxylic acid content.

TPA

Terephthalsäure

IPA

Isophthalsäure

SIPA

5-Sulfoisophthalsäure-Na-Salz

MAL

Maleinsäure

ITAC

Itaconsäure

OSUC

Octenylbernsteinsäure

ODSUC

Octadecenylbernsteinsäure

DOLSUC

Docosenylbernsteinsäure

EG

Ethylenglycol

DD

1,10-Docandiol

HDD

1,2-Hexadecandiol

GMO

Glycerinmonooleat

DIA

Dianol 22 (Akzo),
ethoxyliertes
Bisphenol-A

Abbreviations:

TPA

Terephthalic acid

IPA

Isophthalic acid

SIPA

5-sulfoisophthalic acid sodium salt

TIMES

Maleic acid

ITAC

Itaconic acid

OSUC

Octenyl succinic acid

ODSUC

Octadecenylsuccinic acid

DOLSUC

Docosenyl succinic acid

EG

Ethylene glycol

DD

1,10-docanediol

HDD

1,2-hexadecanediol

GMO

Glycerol monooleate

SLIDE

Dianol 22 (Akzo),
ethoxylated
Bisphenol-A

Example 10-30 Production of graft polymers

3 g of the unsaturated polyesters from Examples 1-9 are dispersed in 30 g of distilled water at room temperature. The dispersion is flushed with nitrogen and heated to 70 ° C. Then 10% of feed 1 and 0.05 g of potassium peroxydisulfate are added. The temperature is raised to 75 ° C. and the remainder of feed 1 and feed 2 are metered in uniformly within 4 hours. When the addition has ended, a further 0.02 g of potassium peroxydisulfate are added and the mixture is stirred at 75 ° C. for 4 hours: Table 2 example polyester Feed 1 composition in% Feed 1 [g] Feed 2 [g] 10th example 1 50 S, 25 AN, 25 EHA 6 15 11 Example 2 50 S, 25 AN, 25 EHA 9 15 12 example 1 47 S, 23 AN, 30 DMA 3rd 10th 13 example 1 47 S, 23 AN, 30 DMA 1.3 10th 14 example 1 50 S, 25 AN, 25 DMA 3rd 10th 15 Example 2 50 S, 25 AN, 25 EHA 6 15 16 Example 3 50 S, 25 AN, 25 EHA 6 15 17th Example 4 50 S, 25 AN, 25 EHA 6 15 18th Example 4 50 S, 25 AN, 25 EHA 9 15 19th Example 4 56 S, 19 AN, 25 EHA 3rd 10th 20th Example 4 56 S, 19 AN, 25 EHA 6 15 21st Example 4 56 S, 19 AN, 25 EHA 9 15 22 Example 4 47 S, 23 AN, 30 EHA 9 15 23 Example 5 50 S, 25 AN, 25 EHA 6 15 24th Example 5 50 S, 25 AN, 25 EHA 9 15 25th Example 5 43 S, 27 AN, 30 EHA 3rd 10th 26 Example 5 43 S, 27 AN, 30 EHA 1.7 10th 27th Example 6 50 S, 25 MAN, 25 EHA 6 10th 28 Example 7 50 S, 25 AN, 25 EHA 6 10th 29 Example 8 50 MMA, 25 AN, 25 EHA 6 10th 30th Example 9 50 S, 25 AN, 5 EHA 10 VDC 6 10th Feed 2: 2% aqueous solution of octadecylsulfonic acid Na salt
S: styrene, EHA: ethylhexyl acrylate, AN: acrylonitrile, DMA: decyl methacrylate, MAN: methacrylonitrile, NMA: methyl methacrylate, VDC: vinylidene chloride

Example 31-52 Production and testing of acceptor elements

The graft polymer dispersions obtained in Examples 10-30 were adjusted to a solids content of 10% with deionized water and used directly for the preparation of ink-receiving layers.

The 10% strength graft polymer dispersions were poured onto a gelatin-coated polyethylene paper in a wet film thickness of 50 μm using a doctor blade. The coatings were dried at room temperature and then annealed at 90 ° C. for 15 minutes. The dry layer thicknesses were approximately 4.5 µm.

Test images were generated on the received elements using a Mitsubishi CP-100 E video printer using the Mitsubishi dye cassette CK-100 S. The color intensity was determined by microdensitometry. The numerical values given are the black and white densities measured on a black surface of the test image without a filter.

The image sharpness was assessed visually immediately after printing, after three days of storage at room temperature and after three days of storage at 57 ° C. and 35% relative humidity. Current No. Graft pole. example Stickiness Sharpness after printing Sharpness after storage density 31 10th 0 ++ ++ 2.11 32 11 1 ++ ++ 2.02 33 12 0 ++ ++ 2.19 34 13 0 ++ ++ 2.28 35 14 0 ++ ++ 2.31 36 15 0 ++ + 1.96 37 16 0 ++ + 1.84 38 17th 1 ++ ++ 1.74 39 18th 1 ++ ++ 1.76 40 19th 1 ++ ++ 1.83 41 20th 1 ++ ++ 1.76 42 21st 1 ++ ++ 1.73 43 22 1 ++ ++ 1.75 44 23 0 ++ ++ 1.86 45 24th 1 ++ ++ 1.80 46 25th 1 ++ ++ 1.83 47 26 1 ++ ++ 1.93 48 27th 0 ++ ++ 1.90 49 28 1 ++ ++ 1.92 50 29 1 ++ ++ 1.82 51 30th 0 ++ ++ 1.95 52 1 3rd not possible to evaluate (Comparison test without grafting) ++ very good
+ good
0 no stickiness
1 extremely low stickiness
2 low stickiness
3 strong stickiness (donor and acceptor material are completely or partially glued together after printing)

Claims (6)

Dye acceptor material for the thermal sublimation printing process with a support and a dye acceptor layer, characterized in that the dye acceptor layer contains a graft polymer from an unsaturated copolyester as the graft base and a vinyl copolymer as the graft pad. Color acceptor material according to claim 1, characterized in that the unsaturated polyester is made up of condensed residues of diols, dicarboxylic acids and optionally hydroxycarboxylic acids, 0.2 to 30 mol% of the condensed residues containing polymerizable double bonds. Color acceptor material according to claim 2, characterized in that 5 to 45 mol% of the condensed residues have one or more aromatic groups. Color acceptor material according to claim 1, characterized in that the vinyl copolymer a) 10-80% by weight of vinyl aromatic and / or (meth) acrylic acid ester with 1-3 C atoms in the alcohol residue
and b) 20-90% by weight of other vinyl monomers is constructed. Color acceptor material according to claim 4, characterized in that the vinyl copolymer a) 10 - 80 wt .-% vinyl aromatic and / or (meth) acrylic acid ester with 1-3 carbon atoms in the alcohol residue b1) 10-70% by weight of (meth) acrylic acid ester with 4-18 C atoms in the alcohol residue b2) 5-40% by weight (meth) acrylonitrile
and b3) 0-30% by weight of other vinyl monomers is constructed. Color acceptor material according to claim 5, characterized in that component b3 comprises hydrophilic monomers.