EP1197345B1 - Recording sheet for ink jet printing - Google Patents

Abstract

Recording material for ink jet printing comprises a support with an ink-absorbing layer comprising a binder, a porous inorganic oxide and a 1,3-cyclohexanedione (I). Recording material for ink jet printing comprises a support with an ink-absorbing layer comprising a binder, a porous inorganic oxide and a 1,3-cyclohexanedione (I) comprising a keto tautomer of formula (Ia) and an enol tautomer of formula (Ib). M = H, metal, or ammonium optionally substituted by one or more optionally substituted 1-18C alkyl groups; R1 = H, 1-12C alkyl, or 2-6C alkyl substituted by CN, COOH, OH or COOR4; R4 = 1-12C alkyl; R2, R3 = H, 1-6C alkyl, or 2-6C alkyl substituted by CN, COOH, OH or COOR5; R5 = 1-12C alkyl.

Description

Technical field

The present invention relates to new stabilizers for recording materials for inkjet printing containing porous inorganic oxides.

State of the art

There are essentially two different methods of inkjet printing, namely continuous and non-continuous ink jet printing.

In continuous ink jet printing, an ink jet becomes pressurized from a nozzle ejected the individual at a certain distance from the nozzle Droplet disintegrates. The individual droplets are, depending on whether an image spot to be printed or not, deflected into a collecting container or up the recording material applied. This happens e.g. B. by the reason given digital data, droplets not required are electrically charged and then deflected into the collecting container in a static electrical field become. The reverse procedure is also possible, with the uncharged Droplets are deflected into the collecting container.

In the non-continuous process, the so-called "drop on demand" the ink drop is only generated when due to the digital data Pixel must be displayed.

Today's inkjet printers have to go faster and faster for economic reasons can print. Recording materials suitable for such printers must be used therefore the inks can absorb particularly quickly. For this purpose Particularly suitable are recording materials, the porous inorganic oxides contain.

Such recording materials available today do not meet all the requirements placed on them. In particular, the shelf life of the images made on these materials needs to be improved. Such images are not particularly stable in contact with outside air, which normally contains sulfur dioxide and, especially in summer, photochemically generated impurities such as ozone and nitrogen oxides. In contact with the outside air, they are very strongly changed or even destroyed within a short period of time. These phenomena are described, for example, in the Hardcopy Supplies Journal, 6 (7), 35 (2000).

To improve the stability of recording materials, the inorganic Containing oxides are, for example, in the patent GB 2,088,777 derivatives of phenols and bisphenols are proposed.

In patent application EP 0'685'345 a Recording material containing porous inorganic oxides, the addition of Dithiocarbamates, thiurams, thiocyanates or sterically hindered amines proposed.

In the patent application EP 0'967'086 the addition of aliphatic hydroxycarboxylic acids with more than two carbon atoms to recording materials proposed for ink jet printing containing porous inorganic oxides, to improve lightfastness.

In patent application EP 0'373'573, polyhydroxybenzene derivatives are used as stabilizers proposed for recording materials for inkjet printing.

In patent application EP 0'674'233 the addition of furan derivatives is cyclic Ketones, lactones, cyclic ketones, cyclic alcohols, cyclic Anhydrides, acid esters and phosphine oxides as stabilizers for recording materials proposed for inkjet printing.

All of these proposed additives improve the stability of recording materials for inkjet printing containing porous inorganic oxides, hardly in contact with polluted outside air.

Stabilizing additives for such recording materials, the porous inorganic Containing oxides must be sufficiently soluble and with the other components the majority of the aqueous coating materials are well tolerated. she must be colorless or at most only slightly colored. Likewise must the additives maintain their quality over a long period of time and also with longer storage of the recording material or the pictures produced on it do not turn yellow. Furthermore, they must be non-toxic and harmless.

There is therefore a need in recording materials that are porous inorganic Oxides contain, in addition to the ink absorption capacity, the ink absorption speed, image quality, water resistance, light resistance etc. especially the shelf life in contact with outside air, the impurities such as ozone, nitrogen oxides or sulfur dioxide can improve.

Summary of the invention

The aim of the invention is to provide recording materials with improved Shelf life in contact with outside air, the porous inorganic Contain oxides in which the image recorded thereon in supervision or Review is considered and which one carrier and at least one ink receiving layer thereon.

It has now surprisingly been found that the shelf life in contact can be significantly improved with outside air if the inventive Recording material unsubstituted or substituted 1,3-cyclohexanedione is added. The on such recording materials according to the invention Pictures produced show the contaminants in contact with outside air such as contains ozone, nitrogen oxides or sulfur dioxide fewer color changes and / or color losses than the corresponding images on recording materials that do not contain such additives.

The recording materials according to the invention for inkjet printing contain in the applied layers next to the porous inorganic oxide and the unsubstituted or substituted 1,3-cyclohexanedione one or more Binder. The unsubstituted or substituted 1,3-cyclohexanedione can in the ink receiving layer containing the porous inorganic oxide or in another layer of the recording material.

1,3-Cyclohexanedione and 2-methyl-1,3-cyclohexanedione are preferred as additives. Other compounds such as reducing agents, organic thio compounds and Inorganic thiocyanates or phenolic compounds can be added to those according to the invention Recording materials can be added.

In addition to the unsubstituted or substituted 1,3-cyclohexanedione, the reducing agent and the organic thio compounds or inorganic Thiocyanates can be added to a reduction catalyst.

Detailed description of the invention

The invention describes a recording material for inkjet printing, the has one or more layers on a carrier, which, in addition to a porous inorganic oxide and binders in an ink-receiving layer, unsubstituted or contain substituted 1,3-cyclohexanedione. The porous inorganic Oxide and the unsubstituted or substituted 1,3-cyclohexanedione can be contained in the same or in different layers.

Such 1,3-cyclohexanediones have already been added to polyvinyl chloride for prevention yellowing or as a heat stabilizer in US Pat. No. 4,252,698 and the patent application JP 51-111'852 proposed.

worin in der Formel Ib (Enolform)

M

für ein Wasserstoffkation, ein Metallkation wie Li, Na oder K, ein Triethanolaminkation oder ein Ammoniumkation steht, das gegebenenfalls einen oder mehrere Alkylreste oder substituierte Alkylreste mit jeweils 1 bis 18 C-Atomen aufweist;

R₁

für Wasserstoff, einen Alkylrest mit 1 bis 12 C-Atomen oder einen substituierten Alkylrest mit 2 bis 6 C-Atomen steht, wobei die Substituenten aus der Gruppe bestehend aus CN, COOH, OH und COOR₄ ausgewählt werden, worin R₄ für einen Alkylrest mit 1 bis 12 C-Atomen steht
und

R₂, R₃

unabhängig voneinander für Wasserstoff, einen Alkylrest mit 1 bis 6 C-Atomen oder einen substituierten Alkylrest mit 2 bis 6 C-Atomen stehen, wobei die Substituenten aus der Gruppe bestehend aus CN, COOH, OH und COOR₅ ausgewählt werden, worin R₅ für einen Alkyl-rest mit 1 bis 12 C-Atomen steht.

The present invention relates to the addition of tautomeric compounds of the formulas la (diketone form) and lb (enol form) to recording materials for inkjet printing which contain a porous inorganic oxide,

where in the formula Ib (enol form)

M

represents a hydrogen cation, a metal cation such as Li, Na or K, a triethanolamine cation or an ammonium cation which may have one or more alkyl radicals or substituted alkyl radicals each having 1 to 18 carbon atoms;

R ₁

represents hydrogen, an alkyl radical having 1 to 12 carbon atoms or a substituted alkyl radical having 2 to 6 carbon atoms, the substituents being selected from the group consisting of CN, COOH, OH and COOR ₄ , in which R _{4 is} an alkyl radical with 1 to 12 carbon atoms
and

R ₂ , R ₃

independently of one another represent hydrogen, an alkyl radical having 1 to 6 carbon atoms or a substituted alkyl radical having 2 to 6 carbon atoms, the substituents being selected from the group consisting of CN, COOH, OH and COOR ₅ , where R _{5 is} is an alkyl radical having 1 to 12 carbon atoms.

M

für ein Wasserstoff-, ein Li-, Na-, K-, Ammonium- oder Triethanolamin-Kation steht;

R₁

für Wasserstoff, einen Alkylrest mit 1 bis 3 C-Atomen oder für einen mit COOR₄ substituierten Alkylrest mit 2 bis 4 C-Atomen steht, worin R₄ für einen Alkylrest mit 1 oder 2 C-Atomen steht

und R₂, R₃

unabhängig voneinander für Wasserstoff, einen Alkylrest mit 1 bis 2 C-Atomen oder einen mit COOR₅ substituierten Alkylrest mit 2 bis 4 C-Atomen stehen, worin R₅ für einen Alkylrest mit 1 oder 2 C-Atomen steht.

Compounds of the formulas Ia and Ib are particularly preferred,
where in the formula Ib (enol form)

M

represents a hydrogen, a Li, Na, K, ammonium or triethanolamine cation;

R ₁

represents hydrogen, an alkyl radical having 1 to 3 carbon atoms or an alkyl radical having 2 to 4 carbon atoms substituted by COOR ₄ , where R _{4 represents} an alkyl radical having 1 or 2 carbon atoms

and R ₂ , R ₃

independently of one another represent hydrogen, an alkyl radical having 1 to 2 carbon atoms or an alkyl radical having 2 to 4 carbon atoms substituted by COOR ₅ , where R _{5 is} an alkyl radical having 1 or 2 carbon atoms.

1,3-Cyclohexanedione and 2-methyl-1,3-cyclohexanedione are particularly preferred as additives.

Such a recording material contains one or more of the compounds mentioned above. Their amount is 1 mg to 5,000 mg / m ² , preferably 50 mg to 600 mg / m ^{2, of} these compounds.

Together with the compounds of the formulas Ia and Ib, reducing agents can also be used such as ascorbic acid or phenylphosphinic acid in the recording material be used.

Together with the compounds of the formulas la and lb, organic compounds can also be used Thio compounds, such as thioglycols or thiocarboxylic acids, in particular Thiodiethylene glycol or thiodipropionic acid, or inorganic thiocyanates, such as ammonium thiocyanate.

It is particularly advantageous if, in addition to the reducing agents, the organic ones Thio compounds or the inorganic thiocyanates still a reduction catalyst such as adding mandelic acid.

The compounds of the formulas Ia and Ib are preferred together with phenolic Compounds such as 2,6-dihydroxybenzoic acid used.

Some of the compounds of the formulas la and lb are known and some are commercially available available or can by known methods (for example, in Houben-Weyl, Methods of organic chemistry, 4th edition, Georg Thieme Verlag Stuttgart, Volume 7 / 2b, page 1617 ff (1976)).

Examples of compounds of the formulas la and lb which are particularly suitable for use in recording materials are those of the formulas (1), (2), (3), (4), (5) and (6)

The additives according to the invention can either be in the form of aqueous, acidic solutions or for example in the form of their Li, Na or K salts, their salt with triethanolamine or their ammonium salt in neutral or basic solution in the Recording material are introduced, wherein the ammonium salt is substituted can be.

If the compounds are not sufficiently water-soluble, they can be replaced by other, known methods can be added to the casting solutions. So can the compounds, for example, in a mixture of water and water-soluble or water-miscible organic solvents such as lower mono- or bis-alcohols, ketones, esters, amides dissolved or be emulsified.

Colloidal silicon oxide, colloidal aluminum oxide or colloidal aluminum oxide / hydroxide can be used as the porous inorganic oxide. Colloidal aluminum oxide or colloidal aluminum oxide / hydroxide are preferred. Particularly preferred as colloidal aluminum oxide is γ-Al ₂ O ₃ and as colloidal AIOOH AIOOH reacted with rare earth salts, as described in patent application EP 0'875'394. This porous aluminum oxide / hydroxide contains one or more elements of atomic number 57 to 71 of the Periodic Table of the Elements, preferably in an amount between 0.4 and 2.5 mole percent based on Al ₂ O ₃ . Particularly preferred as aluminum oxide / hydroxide is pseudo-boehmite, an agglomerate of aluminum oxide / hydroxide of the formula Al ₂ O ₃ • n H ₂ O (n = 1 to 1.5), or pseudo-boehmite reacted with rare earth salts, as also in patent application EP 0'875'394. This porous pseudo-boehmite contains one or more elements of atomic number 57 to 71 of the Periodic Table of the Elements, preferably in an amount between 0.4 and 2.5 mole percent based on Al ₂ O ₃ .

The binders are generally water-soluble polymers. Particularly preferred are film-forming polymers.

The water-soluble polymers include e.g. B. natural or made therefrom modified compounds such as albumin, gelatin, casein, starch, gum arabic, Sodium or potassium alginate, hydroxyethyl cellulose, carboxymethyl cellulose, α-, β- or γ-cyclodextrin etc. When one of the water soluble polymers is gelatin all known types of gelatin can be used, such as acidic Pig skin gelatin or alkaline bone gelatin, acidic or basic hydrolyzed gelatins, as well as substituted gelatins, e.g. B. phthalated, acetylated or carbamoylated gelatin, or reacted with trimellitic anhydride Gelatin.

A preferred natural binder is gelatin.

Synthetic binders can also be used and include, for example Polyvinyl alcohol, polyvinyl pyrrolidone, fully or partially saponified Compounds of copolymers of vinyl acetate and other monomers; Homopolymers or copolymers of unsaturated carboxylic acids such as (Meth) acrylic acid, maleic acid, crotonic acid, etc .; Homopolymers or copolymers from sulfonated vinyl monomers such. B. vinyl sulfonic acid, styrene sulfonic acid etc. Homopolymers or copolymers of vinyl monomers can also be used of (meth) acrylamide; Homopolymers or copolymers of other monomers with ethylene oxide; polyurethanes; polyacrylamides; water soluble nylon polymers; Polyester; polyvinyl lactams; Acrylamide polymers; substituted polyvinyl alcohol; polyvinyl; Polymers of alkyl and sulfoalkyl acrylates and methacrylates; hydrolyzed polyvinyl acetates; polyamides; polyvinylpyridines; polyacrylic acid; copolymers with maleic anhydride; polyalkylene oxides; Copolymers with methacrylamide and copolymers with maleic acid can be used. All of these polymers can can also be used as mixtures.

Preferred synthetic binders are polyvinyl alcohol and polyvinyl pyrrolidone or their mixtures.

These polymers can be made with water-insoluble natural or synthetic high molecular weight compounds are mixed, especially with acrylic latices or styrene acrylic latices.

Although water-insoluble binders are not explicitly claimed, they should water-insoluble polymers are nevertheless regarded as a system component.

The above-mentioned polymers with crosslinkable groups can be prepared using a Crosslinker or hardener converted into practically water-insoluble layers become. Such crosslinks can be covalent or ionic. The networking or hardening of the layers allows a change in the physical layer properties, such as fluid intake, or resistance against shift injuries.

The crosslinkers and hardeners become water-soluble on the basis of the crosslinked Polymers selected.

Organic crosslinkers and hardeners include e.g. B. aldehydes (such as formaldehyde, Glyoxal or glutaraldehyde); N-methylol compounds (such as dimethylol urea or methylol-dimethylhydantoin); Dioxanes (such as 2,3-dihydroxydioxane); reactive vinyl compounds (such as 1,3,5-trisacryloyl-hexahydro-s-triazine or bis- (vinylsulfonyl) methyl ether), reactive halogen compounds (such as 2,4-dichloro-6-hydroxy-s-triazine); epoxides; aziridines; Carbamoyl pyridine compounds or mixtures two or more of these crosslinkers mentioned.

Inorganic crosslinkers and hardeners include, for example, chrome alum, aluminum alum or boric acid.

The layers can also contain reactive substances that act of UV light, electron beams, X-rays or heat the layers network.

The layers can be further modified by adding fillers. Possible fillers are e.g. B. kaolin, Ca or Ba carbonates, silicon dioxide, titanium dioxide, Bentonite, zeolite, aluminum silicate, calcium silicate or colloidal silicon dioxide. Also inert organic particles such as plastic beads can be used. These beads can be made from polyacrylates, polyacrylamides, Polystyrene or various copolymers from acrylates and Styrene exist. The fillers are based on the intended use selected images. Some of these fillers can be transparent Materials are not used. But they can have positive effects in Have oversight materials. Very often you can achieve this with the use of such fillers a desired matt surface.

The recording materials may further contain soluble metal salts, e.g. B. Alkaline earth or rare earth salts.

There is at least one ink-receiving layer in the recording materials according to the invention applied to a support along with any auxiliary layers.

A wide variety of carriers is known and is also used. So can all supports used in the manufacture of photographic materials are used. For example, transparent supports are used from cellulose esters such as cellulose triacetate, cellulose acetate, cellulose propionate, or cellulose acetate / butyrate, polyesters such as polyethylene terephthalate or polyethylene naphthalate, Polyamides, polycarbonates, polyimides, polyolefins, polyvinyl acetals, Polyethers, polyvinyl chloride and polyvinyl sulfones. Preferred are polyesters, especially because of polyethylene terephthalate or polyethylene naphthalate their excellent dimensional stability. With those in the photographic industry opaque supports used can, for example, baryta paper, with polyolefins coated papers, white opaque polyester such as B. Melinex® the DuPont can be used. Polyolefin-coated are particularly preferred Papers or white opaque polyester.

It is advantageous to coat these carriers, in particular polyester, with a Substrate layer to provide the adhesion of the ink receiving layers to improve the wearer. Such substrate layers are in the photographic Industry well known and includes e.g. B. terpolymers of vinylidene chloride, Acrylonitrile and acrylic acid or from vinylidene chloride, methyl acrylate and itaconic acid.

Uncoated papers of various types can also be used as supports that are great in their composition and in their properties May have differences. Pigmented papers and glossy papers can also be used, as well as metal foils such. B. made of aluminum.

The layers can also be made from textile fiber materials, for example Polyamides, polyester, cotton, viscose and wool can be applied.

The additive according to the invention can be added to any layer of the recording material be introduced.

The ink-receiving layers according to the invention are generally made of aqueous solutions or dispersions containing all the necessary components, cast. In many cases, wetting agents are added as sprue aids to to improve the casting behavior and the layer uniformity. Next to her These compounds can also have an effect during the casting process Have an influence on the image quality and can therefore be selected accordingly become. Although such surfactant compounds in the invention are not claimed, they still form an integral part of the Invention.

In addition to the constituents already mentioned, the inventive ones Recording materials contain additional compounds to its properties continue to improve, such as optical brighteners for improvement the degree of whiteness, such as stilbenes, coumarins, triazines, oxazoles or others compounds known to those skilled in the art.

UV absorbers, such as 2-hydroxybenzotriazoles, 2-hydroxybenzophenones, triazine derivatives or cinnamic acid derivatives, can be used to improve the light fastness. The amount of the UV absorber is 200-2000 mg / m ² , preferably 400-1000 mg / m ² . The UV absorber can be introduced into each layer of the recording material according to the invention, but it is particularly advantageous if it is introduced into the top layer.

It is further known that the images produced in ink jet printing are produced by the Addition of radical scavengers, stabilizers, reducing agents and antioxidants can be protected. Examples of such compounds are sterically hindered Phenols, sterically hindered amines, chromanols, ascorbic acid, phosphinic acids and their derivatives, sulfur-containing compounds such as sulfides, mercaptans, Thiocyanates, thioamides or thioureas.

The compounds mentioned can be added to the casting solutions as aqueous solutions be added. If the compounds are not sufficiently water soluble, can be introduced into the casting solutions by other known methods become. For example, the compounds can be mixed with water organic solvents such as lower alcohols, glycols, ketones, esters or amides can be dissolved. It is also possible for the compounds to be fine-grained Dispersions, as oil emulsions, as cyclodextran inclusion compounds or as latex, which contains the compound, in the casting solution.

The recording material according to the invention normally has a dry layer thickness from 0.5 to 100 µm, but especially from 5 to 50 µm.

The casting solutions can be applied to the carrier in various ways become. The casting processes include, for example, extrusion casting, the Air knife casting, the slot casting, the cascade casting and the curtain casting. The casting solutions can also be applied using a spray process. The ink-receiving layers can consist of several individual layers, which can be applied individually one after the other or together. A carrier can also be coated on both sides with ink absorption layers. It is also possible to have an antistatic layer or a layer on the back Apply improvement of flatness. The chosen casting process limits the invention in any way.

It is also possible to use the unsubstituted or substituted 1,3-cyclohexanedione by immersing a recording material in a solution of the unsubstituted or to introduce substituted 1,3-cyclohexanedione into the recording material.

Inks for ink jet printing consist essentially of a liquid Carrier substance and a dye or pigment dissolved or dispersed therein. The liquid vehicle for ink jet printing inks is general Water or a mixture of water and a water-miscible solvent such as ethylene glycol, higher molecular weight glycols, glycerin, Dipropylene glycol, polyethylene glycol, amides, polyvinylpyrrolidone, N-methylyrrolidone, Cyclohexylpyrrolidone, carboxylic acids and their esters, ethers, alcohols, organic Sulfoxides, sulfolane, dimethylformamide, dimethyl sulfoxide, cellosolve, polyurethanes, Acrylates etc.

The non-aqueous ink components generally serve as humectants, auxiliary solvents, Viscosity regulator, penetrant or drying accelerator. The organic compounds mostly have a boiling point that is above that of water. Inks for continuous inkjet printing can further contain inorganic or organic salts to increase the conductivity. Examples of such salts are nitrates, chlorides, phosphates, and the water-soluble ones Salts of water-soluble organic acids such as acetates, oxalates and citrates. The dyes or pigments used to manufacture the together with the invention Inks can be used for recording materials can contain practically all known classes of these colored compounds. Typical examples of dyes or pigments used are in the patent application EP 0 559 324 listed. The recording materials according to the invention can be used with almost all state of the art inks be used.

In addition, the inks can contain other additives such as surface-active Substances, optical brighteners, UV absorbers, light stabilizers, preservatives, Precipitants such as multi-charged metal compounds and polymers Links.

It is very beneficial if unsubstituted or substituted 1,3-cyclohexanedione is introduced into the inks.

The description of the inks is for illustration only and is related to the invention in no way restrictive

The present invention is described in more detail by the following examples, without being restricted in any way.

Examples Example 1 (comparison) Preparation of the casting solution

19.0 g Disperal® (aluminum oxide / hydroxide, available from CONDEA GmbH, Hamburg, Germany) became more aqueous in 51 g at a temperature of 40 ° C Lactic acid solution (0.67%) was dispersed and then 17.1 g of a solution of polyvinyl alcohol (10%, degree of hydrolysis 98-99%, molecular weight 85,000 up to 146,000, available from ALDRICH Chemie, Buchs, Switzerland). The Final weight was adjusted to 100 g with deionized water and the solution Treated with ultrasound for 3 minutes.

molding

150 g / m ^{2 of} this casting solution were applied to a polyethylene-coated paper support at 40 ° C. and the cast support was then dried at 30 ° C. for 60 minutes. 1 m ² of the cast carrier contains, in addition to the other casting additives, 22.2 g of inorganic oxide, calculated as Al ₂ O ₃ , and 2.56 g of polyvinyl alcohol.

Examples 2-12 Preparation of the additional solutions (table 1)

100 g each of the additional solutions were prepared by dissolving the corresponding substance or the corresponding substance mixture in a suitable solvent and then filtering the solution obtained. In the case of solvent mixtures, the ratio is based on weight. example substance Quantity (g) solvent 2 1,3-cyclohexanedione 5.0 Water / methanol 3: 1 3 2-methyl-1,3-cyclohexanedione 5.0 Water / methanol 1: 2 4 1,3-cyclohexanedione 2.5 Water / methanol 1: 2 2-methyl-1,3-cyclohexanedione 2.5 5 1,3-cyclohexanedione 5.0 Water / methanol 3: 1 ascorbic acid 5.0 6 1,3-cyclohexanedione 5.0 Water / methanol 3: 1 ascorbic acid 5.0 mandelic 2.0 7 1,3-cyclohexanedione 5.0 Water / methanol 3: 1 thiodiethylene 5.0 8th 1,3-cyclohexanedione 5.0 Water / methanol 3: 1 thiodiethylene 5.0 mandelic 2.0 9 1,3-cyclohexanedione 5.0 Water / methanol 1: 1 thiodipropionic 5.0 10 1,3-cyclohexanedione 5.0 Water / methanol 3: 1 phenylphosphinic 5.0 11 1,3-cyclohexanedione 5.0 Water / methanol 3: 1 ammonium thiocyanate 1.0 12 1,3-cyclohexanedione 5.0 Water / methanol 3: 1 phenylphosphinic 5.0 mandelic 2.0

1,3-cyclohexanedione and 2-methyl-1,3-cyclohexanedione are available from Acros Organics, Geel, Belgium available. Ascorbic acid, mandelic acid, thiodiethylene glycol, thiodipropionic acid, Phenylphosphinic acid, 2,6-dihydroxybenzoic acid and ammonium thiocyanate are available from Fluka Chemie AG, Buchs, Switzerland.

Production of the casting solutions

19.0 g of Disperal® became more aqueous in 51 g at a temperature of 40 ° C Lactic acid solution (0.67%) and 2.7 g of the corresponding additional solution dispersed and then 17.1 g of a solution of polyvinyl alcohol (10%) was added. The final weight was adjusted to 100 g with deionized water and the solution is sonicated for 3 minutes.

Fonts

150 g / m ^{2 of} each of these casting solutions were applied to a polyethylene-coated paper support at 40 ° C., and the coated support was then dried at 30 ° C. for 60 minutes. 1 m ² of the cast carrier contains, in addition to the other casting additives, 22.2 g of inorganic oxide, calculated as Al ₂ O ₃ , and 2.56 g of polyvinyl alcohol.

Example 13 (comparison with substance from patent application EP 0'685'345) Preparation of the additional solution

100 g of the additional solution of N, N-dimethyldithiocarbamic acid were prepared, by obtaining 5.0 g of the sodium salt of N, N-dimethyldithiocarbamic acid (available at Fluka Chemie AG, Buchs, Switzerland) dissolved in 95 g of water and the obtained Solution was then filtered.

Preparation of the casting solution

19.0 g Disperal® were at a temperature of 40 ° C in 51 g aqueous lactic acid solution (0.67%) and 2.7 g of the additional solution of N, N-dimethyldithiocarbamic acid dispersed and then 17.1 g of a solution of polyvinyl alcohol (10%) added. The final weight was brought to 100 with deionized water g adjusted and the solution treated with ultrasound for 3 minutes.

molding

150 g / m ^{2 of} this casting solution were applied to a polyethylene-coated paper support at 40 ° C. and the cast support was then dried at 30 ° C. for 60 minutes. 1 m ^{2 of} the cast carrier contains, in addition to other casting additives, 22.2 g of inorganic oxide, calculated as Al ₂ O ₃ , and 2.56 g of polyvinyl alcohol.

Castings with those mentioned in the relevant prior art documents Additions 2,6-di-tert-butyl-4-methylphenol (patent GB 2,088,777), sodium thiocyanate (Patent application EP 0'685'345) and 3,4-dimethoxybenzoic acid (patent application EP 0'373'573) could not be produced, since in the with these Additives produced casting solutions precipitated or the viscosity was way too high.

Example 14 (comparison) Preparation of an aqueous dispersion of positively charged SiO ₂

25 g of Aerosil 200 (available from DEGUSSA AG, Frankfurt / Main, Germany) were dispersed at 60 ° C. with stirring in 60 g of aqueous lactic acid (0.67%) with stirring using ultrasound. Then 6.85 g of an aqueous aluminum chlorohydrate solution (47.7%, made from aluminum chlorohydrate of the formula Al ₂ (OH) ₅ Cl • 2.5 H ₂ O, which is available as Locron from Clariant AG, Muttenz, Switzerland) was added and it was 3rd Hours stirred. Then 6.5 g of potassium hydroxide solution (10%) were added and the final weight was adjusted to 100 g.

Preparation of the casting solution

48 g of this aqueous dispersion of positively charged SiO ₂ were diluted with 8 g of water at a temperature of 40 ° C. while stirring and mixed with 27.6 g of a solution of polyvinyl alcohol (10%). After adjusting the final weight with deionized water to 100 g, the solution was treated with ultrasound.

molding

100 g / m ^{2 of} this casting solution were applied to a polyethylene-coated paper support at 40 ° C., and the coated support was then dried at 30 ° C. for 60 minutes. 1 m ² of the cast carrier contains, in addition to the other casting additives, 12 g of positively charged SiO ₂ and 2.8 g of polyvinyl alcohol.

Examples 15-17 Production of the casting solutions

48 g each of the aqueous dispersion of positively charged SiO ₂ from example 14 were stirred at a temperature of 40 ° C. with 27.6 g of a solution of polyvinyl alcohol (10%) and 4 g of the corresponding additional solution (additional solution from example 2 for example 15; additional solution from example 3 for example 16 and additional solution from example 4 for example 17) mixed. After adjusting the final weight with deionized water to 100 g, the solutions were treated with ultrasound.

Fonts

Each 100 g / m ^{2 of} this casting solution was applied to a polyethylene-coated paper support at 40 ° C., and the coated support was then dried at 30 ° C. for 60 minutes. 1 m ² of the cast carrier contains, in addition to the other casting additives, 12 g of positively charged SiO ₂ and 2.8 g of polyvinyl alcohol.

Example 18 (comparison) Preparation of an aqueous dispersion of positively charged SiO ₂

40 Aerosil 200 were dispersed at a temperature of 20 ° C. with stirring in 141.6 g of aqueous lactic acid (1%) with stirring using ultrasound. Then 6.57 g of aluminum chlorohydrate of the formula Al ₂ (OH) ₅ Cl • 2.5 H ₂ O were added and the mixture was stirred at a temperature of 20 ° C. for 3 hours. 8.8 g of potassium hydroxide solution (10%) were then added with thorough stirring, and the final weight was set to 200 g 30 minutes later. The solution contains 20 percent by weight of positively charged SiO ₂ .

Production of aluminum oxide / hydroxide doped with lanthanum (2.2 mol percent based on Al ₂ O ₃ )

50 g of the aluminum oxide / hydroxide Disperal® were dispersed with good mechanical stirring at 20 ° C. in 948 g bidistilled water for 15 minutes. The temperature was then raised to 90 ° C. and stirring was then continued at this temperature for 15 minutes. Then 2.04 g of LaCl ₃ (available from Fluka Chemie AG, Buchs, Switzerland) was added as a solid and stirring was continued for 120 minutes. The solid was filtered off, washed three times with bidistilled water and dried at 110 ° C.

Preparation of the casting solution for the lower layer

19.76 g of the dried solid prepared as described above were with stirring at a temperature of 40 ° C to a mixture of 52.38 g of deionized Water and 0.38 g aqueous lactic acid (90%) added. Subsequently 17.8 g of a solution of polyvinyl alcohol (10%) were added, the solution is treated with ultrasound and the total weight with deionized Water adjusted to 100 g.

Preparation of the casting solution for the upper layer

18.4 g of a solution of polyvinyl alcohol (10%) were added to 40 g of this aqueous dispersion of positively charged SiO ₂ . The solution was adjusted to a final weight of 100 g with deionized water.

molding

263.2 g / m ^{2 of} the casting solution for the lower layer were applied to a transparent polyester support at 40 ° C. and then the cast support was dried at 30 ° C. for 60 minutes.

24.0 g / m ^{2 of} the casting solution for the upper layer were applied to this polyester support cast with the lower layer at 40 ° C., and the cast support was then dried at 30 ° C. for 60 minutes.

1 m ² of the cast support contains, in addition to the other casting additives, 50 g of aluminum oxide / hydroxide doped with lanthanum (2.2 mol percent based on Al ₂ O ₃ ), 1.92 g of positively charged SiO ₂ and 5.13 g of polyvinyl alcohol.

Example 19 Preparation of the casting solution for the upper layer

1.15 g of 1,3-cyclohexanedione were added to 40 g of the aqueous dispersion of positively charged SiO ₂ from Example 18 at a temperature of 40 ° C. with good stirring. Then 18.4 g of a solution of polyvinyl alcohol (10%) were added. The solution was adjusted to a final weight of 100 g with deionized water.

Pouring solution for the lower layer and casting

The casting solution for the lower layer and the casting were as in Example 18 described.

The following procedure was used to determine resistance to outside air of the recording materials described here:

The recording materials according to the invention were printed using an inkjet printer EPSON STYLUS ™ COLOR 750 in transparent mode (720 dpi) with original inks color fields printed with the tri-color black.

The printed samples were in average daylight from 1000 - 2000 Lux open on a table with moderate circulation of outside air during 2 Weeks left.

The loss of density was measured with an X-Rite® densitometer. He is called percentage loss of density of the three-color black with 50% density in the red channel based on the original density.

Results

The density losses obtained under these test conditions for recording materials according to the invention which contain the porous inorganic aluminum oxide / hydroxide Disperal® are summarized in Table 2: example yellowing Color density loss in% 1 No 36 2 No 6 3 No 22 4 No 12 5 No 8th 6 No 9 7 No 5 8th No 6 9 weak 6 10 No 8th 11 No 8th 12 No 6 13 No 28

It can be seen immediately from the results in Table 2 that recording materials for inkjet printing, which is the porous inorganic alumina / hydroxide Disperal® and the additives according to the invention contain (examples 2 - 12), much lower density losses in the red channel (severe destruction of the Cyan dye combined with a color change of the black color fields of black to brown-orange) show as a corresponding recording material, that no such addition (example 1) or an already known addition (Example 13) contains. The recording materials according to the invention show no or at most a slight yellowing.

The density losses obtained under these test conditions for recording materials according to the invention which contain positively charged SiO ₂ are summarized in Table 3: example yellowing Color density loss in% 14 No 21 15 No 12 16 No 16 17 No 17

It can be seen immediately from the results in Table 3 that recording materials for inkjet printing which contain positively charged SiO ₂ and the additives according to the invention (Examples 15-17), lower density losses in the red channel (severe destruction of the cyan dye combined with a color change in the black color fields of black to brown-orange) show as a corresponding recording material that does not contain such an additive (Example 14). The recording materials according to the invention show no slight yellowing.

The density losses obtained under these test conditions for recording materials according to the invention which contain aluminum oxide / hydroxide doped with lanthanum and positively charged SiO ₂ are summarized in Table 4: example yellowing Color density loss in% 18 No 48 19 No 11

It can be seen immediately from the results in Table 4 that the recording material for inkjet printing, the aluminum oxide / hydroxide doped with lanthanum and positively charged SiO ₂ and the addition of 1,3-cyclohexanedione according to the invention (Example 19) contains much lower density losses in the red channel shows as a corresponding recording material that does not contain such an additive (Example 18). The recording material according to the invention showed no yellowing.

Claims (10)

1. Recording sheet for ink jet printing, having coated onto a support at least one ink receiving layer comprising binders and an inorganic porous oxide, characterized in that said recording sheet contains tautomeric compound of formulas la (diketo form) and Ib (enol form)

   

   wherein in formula Ib (enol form)

   M

   represents a hydrogen cation, a metal cation or an ammonium cation optionally substituted by one or more alkyl or substituted alkyl groups each having from 1 to 18 C atoms;

   R₁

   represents hydrogen, alkyl with 1 to 12 C atoms or substituted alkyl with 2 to 6 C atoms, wherein the substituents are selected from the group consisting of CN, COOH, OH and COOR₄, where R₄ represents alkyl with 1 to 12 C atoms

   and R₂, R₃

   independently represent hydrogen, alkyl with 1 to 6 C atoms or substituted alkyl with 2 to 6 C atoms, wherein the substituents are selected from the group consisting of CN, COOH, OH and COOR₅, where R₅ represents alkyl with 1 to 12 C atoms.

2. Recording sheet according to claim 1, characterized in that

   M

   represents a hydrogen cation, a Li cation, a Na cation, a K cation, an ammonium or a triethanolamine cation;

   R₁

   represents hydrogen, alkyl with 1 to 3 C atoms or alkyl substituted by COOR₄ with 2 to 4 C atoms, where R₄ represents alkyl with 1 or 2 C atoms;
   and

   R₂, R₃

   independently represent hydrogen, alkyl with 1 or 2 C atoms or alkyl with 2 to 4 C atoms substituted by COOR₅, where R₅ represents alkyl with 1 o 2 C atoms.

3. Recording sheet according to claim 1, characterized in that

   M

   represents a hydrogen cation;

   R₁

   represents hydrogen or methyl
   and

   R₂, R₃

   represent hydrogen.

4. Recording sheet according to claims 1 to 3, characterized in that said recording sheet contains in addition reducing agents, phenolic compounds, organic thio compounds or inorganic thiocyanates.
5. Recording sheet according to claim 4, characterized in that it contains in addition a reduction catalyst.
6. Recording sheet according to claims 1 to 5, characterized in that the porous inorganic oxide is colloidal aluminium oxide, colloidal aluminium oxide/hydroxide or positively charged silicium dioxide.
7. Recording sheet according to claims 1 to 5, characterized in that the porous inorganic oxide is colloidal γ-Al₂O₃ or pseudo-boehmite.
8. Recording sheet according to claims 1 to 5, characterized in that the porous inorganic oxide is AIOOH or pseudo-boehmite comprising one or more of the elements of the rare earth metal series of the periodic system of the elements with atomic numbers 57 to 71 in an amount of from 0.4 to 2.5 mole percent relative to Al₂O₃.
9. Recording sheet according to claims 1 to 8, characterized in that the binder is selected from gelatin, polyvinyl alcohol and polyvinyl pyrrolidone or mixtures thereof.
10. Recording sheet according to claims 1 to 9, characterized in that the support is selected from coated or uncoated paper, transparent or opaque polyester or fibrous textile materials.