BACKGROUND OF THE ART In recent years, the use of ink-jet system to generate images has rapidly growth. The improvement in both printers and ink-jet recording media performances allows to obtain images similar to conventional silver halide photographic ones. At the same time, due to spreading speed increase in printing systems, there is the need to use recording media able to absorb all ink volumes in very short time. The ink high speed absorptivity can be achieved using an ink-jet recording material comprising a porous layer which is able to rapidly remove the fresh spread ink from the surface of the material, while the absorption capacity can be adjusted varying the thickness of the receiving layer.

Even if the ink-jet record materials having porous layers present a better ink absorptivity than ink-jet record materials utilizing swelling system layers, the images printed on porous system may suffer of oxidation deterioration of coloring matter component under natural air exposure. The gas circulation in porous materials supplies a continuous flux of oxidizing compounds, such as nitrogen oxides, sulfur oxides, oxygen or ozone gas, that are directly in contact with the coloring matter in the porous layer.

Accordingly, images obtained by ink-jet recording materials have inferior properties in terms of storage characteristics, such as light resistance, water resistance, gas resistance color fading, compared to images obtained by silver halide photographic materials.

Various attempts have been done in the art to solve said color fading problem.

EP 1,186, 439 discloses a surface treatment method for images recorded on a recording medium, which can improve the weather resistance characteristics of the images, such as light resistance and air resistance. Said method is characterized by subjecting said images recorded to an after-treatment, such as spray treatment, coating treatment, immersion treatment, to form an overcoat layer applied onto the surface of the images recorded. This overcoat layer contains an aqueous solution containing a water-soluble resin, a light resistance improving agent and an ink fixing agent; the overcoat layer protects the surface of said recorded images preventing the gas present in the air to penetrate into

the recorded images, and thus improving the color fading due to light and air oxidation.

Another after-printing method to protect ink-jet prints is disclosed in US Patent Application No. 2003/0117471, wherein a process for applying a protective layer to an ink- jet print is disclosed, wherein the process comprises printing an image on a medium by inlc- jet technology and then spraying on said medium a solution of a protective material in a solvent. hi some cases, a color fading inhibitor compound has been added to the ink composition. European Patent 875,544, for example, discloses an ink composition comprising a colorant, water, a water-soluble organic solvent, and a fine particle polymer latex, wherein the polymer constituting the latex particles have a film-forming property and, at the same time, an ultraviolet absorbing capacity and/or a light stabilizing capability ; Japanese Patent application 11-315,234 discloses an ink composition containing a triazine compound and a sterically hindered amine compound ; Japanese Patent application 05- 239,389 discloses a recording liquid comprising a dye, pure water and a light stabilizer capable of obtaining high-grade stabilized images.

However, the cited above tentative problem solutions to include a color fading inhibitor compound into an ink-jet ink composition have the disadvantage that it is difficult to find the proper compromise between the ink pH level and the single compounds without occurring in negative interactions among them.

Thus, it is desirable to keep the color fading inhibitor compound apart from the ink- jet ink composition to have the possibility to choose the proper amount of color fading inhibitor compound to be applied to said microporous material to form an image having improved air resistance and color fading, independently of the amount and type of components included in said ink composition.

SUMMARY OF THE INVENTION In a first aspect, the present invention refers to an ink-jet printing method for forming a durable image on an ink-jet recording microporous material, comprising a support and at least one ink receiving microporous layer coated thereon, by means of an ink-jet printing apparatus comprising at least one ink-jet printing cartridge containing ink-jet ink compositions, said method comprising the steps of applying an aqueous solution comprising a color fading inhibitor compound to said ink-jet recording microporous material immediately before, during or immediately after that said ink-jet ink compositions are applied to said microporous material to form an image.

In a second aspect, the present invention refers to a cartridge to be used in an ink-jet printing apparatus, wherein said cartridge contains an aqueous solution comprising a color fading inhibitor compound to be applied to an ink-jet recording microporous material immediately before, during or immediately after ink-jet ink compositions to form an image.

In a third aspect, the present invention refers to an ink-jet printing apparatus containing at least one cartridge containing ink-jet ink compositions and an additional cartridge, wherein said additional cartridge contains an aqueous solution comprising a color fading inhibitor compound to be applied to an ink-jet recording microporous material immediately before, during or immediately after that said ink-jet ink compositions are applied to said microporous material to form an image.

DETAILED DESCRIPTION OF THE INVENTION The printing apparatus used in the present invention, such as ink-jet printer or ink- jet plotter, mainly includes one or several ink jet cartridges in which one or plural ink-jet ink compostions are kept, and a printer main body with a print head to-carry out actual printing operations on a printing medium. In the present invention, the term"ink composition"refers to black into compositions in the case of monochromic printing and color ink compositions in the case of color printing, specifically yellow, magenta, and cyan ink compositions, and, optionally, black ink compositions. In case of color ink compositions, several ink-jet cartridges can be used, for example, for each of yellow, magenta, cyan, and black color. Said cartridges are attached such that they can be removed by hand without destroying any of the structure used for the attaching, or without the use of tools. The removable and nonfixed attachment allows the cartridges to be easily and quickly removed and replaced with fresh cartridges. The structure for removable attachment may be any suitable structure known in the art, such as for example, mounting structure on the cartridge, such as curved or angular mating surfaces in the cartridge housing, sliding surfaces, grooves, knobs, locks, apertures, sprung members, and the like, that may interact or interlock or mate, with opposing or mating structures associated on the printing apparatus. The ink jet printing process can be performed according to any of the well-known techniques, such as the continuous printing method, the thermal jet method and the piezo method. The print head receives inks from the ink-jet cartridges through an ink supply tube and in the print head a number of ejection orifices for discharging the inks as ink droplets are formed. The print head is moved along a carriage by means of, for example, a timing belt driven by a motor. On the other hand, the recording medium is placed by a platen and a guide at a position facing the print head. The print head transfers

the inks fed from the ink cartridges onto the printing medium, such as printing paper, so as to implement printing on the printing medium. Typical printing apparatus as above are disclosed, for example, in US Patent Nos. 6,585, 362; 6,590, 012; 6,619, 791; 6,631, 967; 6,676, 734 and in European patent Application No. 1,380, 622. The print head and the ink- jet cartridges can be separated from each other, but they can also be integrally combined.

When the ink in the ink-jet cartridge is exhausted, the ink-jet cartridge can be replaced by a new one.

The printing apparatus of the present invention also includes at least an additional cartridge. The additional cartridge may have the same shape, dimension and functional characteristics of previous described ink-jet ink cartridges, but it is physically separated from the ink cartridges. The additional cartridge contains an aqueous solution comprising a color fading inhibitor compound. The solution may comprise an additional organic solvent and/or an inorganic or organic acid.

Preferably, the color fading inhibitor compounds contained in said solution are represented by the following Formula I : Formula I wherein Rl to Rlo, being the same or different, each is an allcyl group having from 1 to 5 carbon atoms; X is a divalent linking group; m and n, equal or different, are 0,1 or 2; Z is Y or is an alkyl group having from 1 to 12 carbon atoms, and Y is represented by formula II, Formula II

wherein Rl l and Rl2 each being an allcyl group having from 1 to 6 carbon atoms.

In previous Formula I, Ri to Rio, being the same or different, each represents a straight or branched alkyl group having from 1 to 5 carbon atoms, such as, for example, methyl group, trifluoromethyl group, ethyl group, propyl group, isopropyl group, butyl group, tert. -butyl group. Preferred examples of alkyl groups represented by Rl to Rio are methyl groups or ethyl groups.

X, when present, is a divalent linking group, such as, for example, straight chain, branched chain or cyclic alkylen, arylene, aralkylene, oxy, oxo, thio, sulfonyl, sulfoxy, amino, imino,, ulfonamido, carbonamido, carbonyloxy, urethanylene and ureylene groups and combinations thereof such as sulfonamidoalkylene or carbonamidoallcylene ; m and n, equal or different, are 0,1 or 2. Preferred examples of divalent linking groups are allcylene groups.

Z can be represented by Formula II or by an alkyl group having from 1 to 12 carbon atoms, such as, for example, methyl group, trifluoromethyl group, ethyl group, propyl group, isopropyl group, butyl group, tert. -butyl group, pentyl group, octyl. group, nonyl group. Preferred examples of alkyl groups represented by Z are allcyl groups having froml to 6 carbon atoms.

In previous Formula II, Rll and R12, being the same or different, each represents a straight or branched alkyl group having from 1 to 6 carbon atoms, such as, for example, methyl group, trifluoromethyl group, ethyl group, propyl group, isopropyl group, butyl group, tert. -butyl group, pentyl group, hexyl group. Preferred examples of alkyl groups represented by Rll and R12 are methyl groups, ethyl groups, butyl group or tert.-butyl groups.

More preferably, color fading inhibitor compounds contained in said solution are represented by the following Formula III: Formula III

wherein, Y, Rl and R6 are as above and Alk is an allcyl group having from 1 to 12 carbon atoms, such as, for example, methyl group, trifluoromethyl group, ethyl group, pro- pyl group, isopropyl group, butyl group, tert. -butyl group, pentyl group, hexyl group.

Preferred examples of allcyl groups represented by Alk are alkyl groups having from 1 to 6 carbon atoms, such as, for example are methyl groups, ethyl groups, butyl group or tert.- butyl groups.

When in the present invention the term"group"is used to define a chemical compound or substituent, the described chemical material comprises the basic group, ring or residue and that group, ring or residue with conventional substitutions. When on the contrary the term"units"is used, only the chemical unsubstituted material is intended to be included. For instance, the term"allcyl group"comprises not only those allcyl units such as methyl, ethyl, butyl, octyl, stearyl, etc. , but even those units bearing substituents such as halogen atoms, cyano, oxydryl, nitro, amino, carboxilate groups. The term"allyl wuts"on the contrary comprises only methyl, ethyl, stearyl, cyclohexyl.

Examples of color fading inhibitor compounds useful in the present invention are represented, but not limited to, by the following examples.

Compound (1) Compound (2)

Compound (3)

Compound (4) Compound (5) Compound (6)

The color fading inhibitor compounds useful in the present invention are commercially available, for example, from Ciba Specialty Chemicals Inc, Basel, Switzerland.

The color fading inhibitor compound is contained in the solution at a concentration of from 0.1 to 40 % by weight, preferably from 0.2 to 30 % by weight more preferably from 0.5 to 20 % by weight.

The acids contained in the solution are preferably selected from the group consisting of the acids able to neutralize the aminic groups of the color fading inhibitor compounds cited above and to solubilize said compounds. In particular said acids are selected from the group consisting of organic or inorganic acids; typical organic acids include sulfonic acids, such as, for example, ethanesulfonic acid; monocarboxylic acids, such as, for example, formic acid, acetic acid, propionic acid, butyric acid, valeric acid; dicarboxylic acids, such as, for example, oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid, maleic acid, fumaric acid, phthalic acid, isophthalic acid, terephthalic acid; polycarboxylic acids, such as, for example, lactic acid, malic acid, citric acid and ethylenediaminetetraacetic acid. Typical inorganic acids include hydrochloric, phosphoric acid, nitric acid, sulfuric acid, sulfurous acid, perchloric acid. More preferably, the acids contained in said solution are selected from the group consisting in hydrochloric acid, nitric acid, sulfuric acid, acetic acid.

The acid compound is contained in the solution at a concentration able to provide a pH of the solution comprised between 1 to 9, preferably between 2 and 5.

The organic solvents preferably added to the aqueous solution are preferably selected from the group consisting of the low-boiling water-soluble organic solvents, such as those organic solvents being miscible with water at least at 50%. Examples of useful low-boiling water-soluble organic solvents include, but are not limited to an alcohol, such as, for example, methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, n-butanol, sec- butanol, tert-butanol, iso-butanol, n-pentanol ; a ketone, such as, for example, methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, acetone ; an amide, such as, for example, formamide, N, N-dimethylformamide, N, N-dimethylacetamide or N- methylpyrrolidone. Monohydric alcohols are particularly preferred. Said low-boiling organic solvents may be used in admixture of two or more. The amount of the low-boiling organic solvents added is preferably in the range of from 0.1 to 20 % by weight, more preferably in the range of from 1 to 10 % by weight.

The solution can additionally comprises a humectant to help preventing said solution from drying out or crusting in the orifices of the print head. Examples of humectants include, but are not limited to, as disclosed for example in US Patent No.

6,585, 362: glycols, such as, for example, ethylene glycol (EG), diethylene glycol (DEG), triethylene glycol (TEG), propylene glycol (PG), dipropylenglycol (DPG), polyethylenglycole (PEG), polypropylenglycole (PPG); monoether glycols, such as, for example, ethylenglycolemonomethyether (EGmME), ethylenglycolemonoethylether (EGmEE), diethylenglycolemonomethylether (DGmME), diethylenglycolemonoethylether (DGmEE), triethylenglycolemonomethylether (TGmME), triethylenglycolemonobuthylether (TEGmBE), diethylenglycolemonobuthylether (TEGmBE), triethylenglycolemonoethylether (TEGmEE) ; diether glycols, such as, for example, triethylenglycoledimethylether (EGdME), triethylenglycolediethylether (EGdEE); divalent alcohol, such as, for example, 1,3-propandiol, 1,4-butandiol, 1, 3-butandiol, 1,2- butandiol, 1,5-pentandiol, 1,4-pentandiol, 1, 3-pentandiol, 1,2-pentandiol, 1,5-exandiol, 1,4- exandiol, 1,3-exandiol, 1,2-exandiol ; trivalent alcohols, such as, for example, glycerine and 1,2, 6-exantriol; ethanolamine, such as, for example, N, N-dimethylethanolamine, N, N- diethylethanolamine, diethanolamine, triethanolamine, triisopropanolamine, and N ; N- butyldiethanolamine; nitrogen-containing compounds, such as, for example, urea, 2- pyrrolidinone, 3-pyrrolidinone, N-methyl-2-pyrrolidinone, imidazolidinone and 1,3- dimethyl-2-imidazolidinone; and sulfur-containing compounds such as, for example, dimethyl sulfoxide and tetramethylene sulfone, or-mixtures thereof. Preferred humectants are glycols and divalent alcohol. The humectant is used in the solution at a concentration of from about 3 to about 40 % by weight, preferably from about 5 to about 30 % by weight.

Surfactants and anti-bacteric agents may be added to the solution to adjust the surface tension to an appropriate level for the jet realization. The surfactants may be anionic, cationic, amphoteric or nonionic and used at concentration of from 0.01 to 1 % by weight of the solution. Preferred surfactants include Surfynol 465 (available from Air Products <BR> <BR> <BR> Corp. ) and TergitolTM 15-S-5 (available from Union Carbide Co. ). Anti-bacteric agents may be added to said solution to prevent the formation and the growth of microorganisms such as molds, fungi, etc. in aqueous solutions. A preferred biocide for the solution employed in the present invention is Proxel GXL (Avecia Corp. ) at a final concentration of 0.0001-0. 5 wt. %.

Ink-jet ink compositions used in the present invention are conventional ink compositions known in the art generally, such as those describe, for example, in US Patent

Nos. 6,590, 012 and in European Patent application No. 1,125, 760. Generally, the ink compositions basically comprises at least a colorant, a dispersant, a water-soluble organic solvent, and water.

The colorant contained in the ink compositions of the present invention may be either a dye or a pigment. Various dyes commonly used in ink jet inks, such as direct dyes, acid dyes, foodstuff dyes, basic dyes, reactive dyes, disperse dyes, vat dyes, soluble vat dyes, and reactive disperse dyes, may be used as the dye. The pigment is not particularly limited, and any of inorganic and organic pigments may be used as the pigment. Examples of the inorganic pigment include, in addition to titanium oxide and iron oxide, carbon blacks produced by known processes, such as contact, furnace, and thermal processes.

Examples of the organic pigment include azo pigments (including azo like, insoluble azo pigment, condensed azo pigment, and chelate azo pigment), polycyclic pigments (for example, phthalocyanine, perylene, perinone, anthraquinone, quinacridone, dioxazine, thioindigo, isoindolinone, and quinophthalone pigments), dye chelates (for example, basic dye chelates and acid dye chelates), nitro pigments, nitroso pigments, and aniline black.

In particular, carbon blacks usable for black inlcs include, but are not limited to : No.

2300, No. 900, MCF 88, No. 33, No. 40, No. 45, No. 52, MA7, MAB, MA100, No. 2200B and the like, manufactured by Mitsubishi Chemical Corporation; Raven 5750, Raven 5250, Raven 5000, Raven 3500, Raven 1255, Raven 700 and the like, manufactured by Columbian Carbon Co. , Ltd.; Regal 400R, Regal 330R, Rega 1660R, Mogul L, Monarch 700, Monarch 800, Monarch 880, Monarch 900, Monarch 1000, Monarch 1100, Monarch 1300, Monarch 1400 and the like, manufactured by Cabot Corporation ; and Color Black FW1, Color Black FW2, Color Black FW2V, Color Black FW18, Color Black FW200, Color Black S150, Color Black S160, Color Black S170, Printex 35, Printex U, Printex V, Printex 140U, Special Black 6, Special Black 5, Special Black 4A, and Special Black 4, manufactured by Degussa.

Pigments usable for yellow inks include C. I. Pigment Yellow 1, C. I. Pigment Yellow 2, C. I. Pigment Yellow 3, C. I. Pigment Yellow 12, C. I. Pigment Yellow 13, C. I.

Pigment Yellow 14C, C. I. Pigment Yellow 16, C. I. Pigment Yellow 17, C. I. Pigment Yellow 73, C. I. Pigment Yellow 74, C. I. Pigment Yellow 75, C. I. Pigment Yellow 83, C. I.

Pigment Yellow 93, C. I. Pigment Yellow 95, C. I. Pigment Yellow 97, C. I. Pigment Yellow 98, C. I. Pigment Yellow 114, C. I Pigment Yellow 128, C. I. Pigment Yellow 129, C. I.

Pigment Yellow 151, C. I. Pigment Yellow 154, C. I. Pigment Yellow 155, C. I. Pigment Yellow 180, and C. I. Pigment Yellow 185.

Pigments usable for magenta inlcs include C. I. Pigment Red 5, C. I. Pigment Red 7, C. I.

Pigment Red 12, C. I. Pigment Red 48 (Ca), C. I. Pigment Red 48 (Mn), C. I. Pigment Red 57 (Ca), C. I. Pigment Red 57 : 1, C. I. Pigment Red 112, C. I. Pigment Red 123, C. I. Pigment Red 168, C. I. Pigment Red 184, and C. I. Pigment Red 202.

Pigments usable for cyan inks include C. I. Pigment Blue 1, C. I. Pigment Blue 2, C. I. Pigment Blue 3, C. I. Pigment Blue 15: 3, C. I. Pigment Blue 15: 34, C. I. Pigment Blue 16, C. I. Pigment Blue 22, C. I. Pigment Blue 60, C. I. Vat Blue 4, and C. I. Vat Blue 60.

For these pigments, the particle diameter is about 500 nm or less, preferably about 200 nm or less, more preferably about 100 nm or less.

The content of the colorant in the ink composition according to the present invention is preferably about 1 to 20 % by weight, more preferably 1 to 10 % by weight, based on the ink composition. When the colorant content falls within the above range, good print stability can be realized in ink jet recording.

Previously described pigment is added, to the ink composition, in the form of a pigment dispersion prepared by dispersing the pigment in an aqueous medium with the aid of a dispersant. Preferred dispersants include those commonly used in the preparation of a dispersion of a pigment, for example, a polymeric dispersant. Preferred examples of polymeric dispersants usable herein include naturally occurring polymers, and specific examples thereof include: proteins, such as glue, gelatin, casein, and albumin; naturally occurring rubbers, such as gum arabic and tragacanth ; glucosides, such as saponin ; alginic acid and alginic acid derivatives, such as propylene glycol alginate, triethanolamine alginate, and ammonium alginate; and cellulose derivatives, such as methyl cellulose, carboxymethyl cellulose and hydroxyethyl cellulose. Preferred polymeric dispersants usable herein include synthetic polymers, and examples thereof include polyvinyl alcohols, polyvinyl pyrrolidones, acrylic resins, such as polyacrylic acid, acrylic acid/acrylonitrile copolymer, potassium acrylate/acrylonitrile copolymer, vinyl acetate/acrylic ester copolymer, and acrylic acid/acrylic ester copolymer, styrene/acrylic resins, such as styrene/acrylic acid copolymer, styrene/methacrylic acid copolymer, styrene/methacrylic acid/acrylic ester copolymer, styrene/a-methylstyrene/acrylic acid copolymer, and styrene/a-methylstyrene/acrylic acid/acrylic ester copolymer, styrene/maleic acid copolymer, styrene/maleic anhydride copolymer, vinylnaphthalene/acrylic acid copolymer, vinylnaphthalene/maleic acid copolymer, and vinyl acetate copolymers, such as vinyl acetate/ethylene copolymer, vinyl acetate/fatty acid/ethylene copolymer, vinyl

acetate/maleic ester copolymer, vinyl acetate/crotonic acid copolymer, and vinyl acetate/acrylic acid copolymer, and salts of the above polymers.

The content of the dispersant in the ink composition is about O. 1 to 20 % by weight, preferably about 0.1 to 10 % by weight.

The ink composition used in the present invention comprises a water-soluble organic solvent. The water-soluble organic solvent is preferably a low-boiling organic solvent, and examples thereof include methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, n-butanol, sec-butanol, tert-butanol, iso-butanol, and n-pentanol. Monohydric alcohols are particularly preferred. The low-boiling organic solvent has the effect of shortening the time taken for drying the ink. The amount of the low-boilimg organic solvent added is preferably in the range of from 0.1 to 30 % by weight, more preferably in the range of from 5 to 10 % by weight, based on the ink.

The ink compositions used in the present invention can further comprise wetting agents and surfactants; in addition the ink compositions can also contain, saccharide, a tertiary amine, an alkali hydroxide, or ammonia to prevent agglomeration of the colorant and an increase in viscosity of the ink even after storage for a long period of time.

In the present invention, the solution comprising a color fading inhibitor compound is applied to the ink-jet recording microporous material immediately before, during or immediately after the time in which the ink composition is applied to said microporous material. That means that the solution comprising a color fading inhibitor compound is jetted from the additional cartridge to the ink-jet recording microporous material during the printing process in the printing apparatus just before, at the same time, or just after the ink composition is jetted from the ink-jet cartridges. In a preferred aspect of the invention, the solution comprising a color fading inhibitor compound is applied to the ink-jet recording microporous material before the ink-jet ink compositions are applied to the microporous material to form an image.

The ink-jet recording microporous material used in the present invention, onto which a solution containing a color fading inhibitor compound and ink-jet ink compositions are applied to form an image, comprises a support and at least one porous ink receiving layer.

Said support includes any conventional support'for ink jet recording sheet. As a support, a transparent or opaque support can be used according to the final use of the ink jet recording material. As transparent support, any conventional support, such as a film or plate of polyester resins, cellulose acetate resins, acryl resins, polycarbonate resins,

polyvinyl chloride resins, poly (vinylacetals) resins, polyethers resins, polysulfonamides resins, polyamide resins, polyimide resins, cellophane or celluloid and a glass plate can be used in the present invention. The thickness of the transparent support is preferably from 10 to 200 micrometer. As the opaque support, any conventional one such as paper, coat paper, synthetic paper, resin-covered paper, pigment-containing opaque film or foaming film can be used in the invention.

The base material may be subjected to a surface treatment such as a corona discharge treatment for improving its adhesiveness to the ink-receiving layer, or provided with an adhesion improving layer as an under coat. Further, a curl-preventing layer such as a resin layer or a pigment layer may be provided on the back surface of the base material or at a desired position thereof to prevent curling.

Said at least one porous ink receiving layer coated onto the support base comprises inorganic pigment fine particles and binder resin.

The inorganic pigment fine particles contained in the porous layer may be inorganic pigment fine particles which are insoluble or hardly soluble in water. Specifically, the inorganic pigment fine particles can be exemplified by inorganic pigments such as calcium carbonate, kaolin, talc, calcium sulfate, barium sulfate, titania, zinc oxide, zinc carbonate, aluminum silicate, alumina hydrate, magnesium silicate, calcium silicate and silica, any of which may be used alone and also in combination. Pigments particularly preferable from the viewpoint of ink absorptivity and image suitability such as image resolution, include alumina hydrate, silica and calcium carbonate.

Alumina hydrate may be represented by the formula A1203. nH20 ; specifically, the alumina hydrate may be, for example, gibbsite, bayerite, nordostrandite, boehmite, diaspore or pseudoboehmite. Alumina hydrate, and in particular boehmite or pseudo-boehmite, (wherein n is from 1.0 to 2.0) is preferably used in the ink-jet recording material used in the present invention. Said alumina hydrate, as described for example in EP patent application No. 636,489, can be produced by any conventional method such as the hydrolysis of aluminum alkoxide or sodium aluminate. Rocek, et al. [Collect Czech. Chem. Commun., Vol. 56,1253-1262 (1991) ] have reported that the pore structure of aluminum hydroxide is affected by deposition temperature, pH of the solution, aging time and surfactants used.

The shape of the alumina hydrate can be in the form of a needle or in the form of a flat plate (as described in the literature by Rocek J. , et al., Applied Catalysis, Vol. 74,29-36 (1991), the latter being particularly preferred for the reasons that better dispersibility can be obtained and because the orientation of particles of the alumina hydrate in the form of a flat

plate becomes random when forming an ink-receiving layer, so that the range of the pore radius distribution widens. The average particle diameter of the alumina hydrate is preferably in the range from 10 to 200 mn, preferably from 50 to 150 nm. In the present invention, the dry content of the alumina particles in the micorporous ink-receiving layer preferably is from 10 to 95 % by weight, more preferably from 15 to 90 % by weight; the ink-receiving layer preferably comprises from 10 to 80 g/m2, more preferably from 15 to 60 g/m2 of alumina particles. The solvent is preferably water.

The silica may include natural silica, synthetic silica, amorphous silica, and chemically modified silica compounds, any of which may be used without any particular limitations, but particularly preferable is synthetic fine particulate silica with a specific surface area having preferably from 20 to 700 g/m2 according to the BET method, and by use of the silica with such specific surface area, excellent color forming characteristic of the water-soluble dye in ink, optimum shape and size of ink dots can be accomplished.

Silica particles are described, for example, in US 5,612, 281 and EP 813,978, which discloses ink-jet recording materials using synthetic silica fine particles prepared by a gas phase process, giving ultrafine particles having an average particle size from several nm to several tens nm, and having characteristics of giving high glossiness and high ink- absorption properties. A method for producing a positively charged colloidal silica sol is also disclosed, for example, in EP 1,112, 962 and JP-B-47-26959, the method comprising coating the silica surface with alumina. By this method, it is possible to obtain a silica sol having the surface coated with alumina, which is excellent in transparency and stability.

The content of silica should preferably be at least 10 % by weight, more preferably at least 30 % by weight in the micorporous ink-receiving layer.

The calcium carbonate may include heavy calcium carbonate, light calcium carbonate and colloidal calcium carbonate, any of which may be used.

The binder resin in said porous ink-receiving layer may be, for example, polyvinyl alcohol, silanol modified polyvinyl alcohol, polyvinyl acetate, oxidized starch, etherified starch, a cellulose derivative such as carboxymethyl cellulose or hydroxyethyl cellulose, casein, gelatin, acidic gelatin, soybean protein or, maleic anhydride resin, a copolymer latex of conjugated diene type such as a styrene-butadiene copolymer or a methylmethacrylate-butadiene copolymer ; an acrylic polymer latex of acrylic type such as a polymer or a copolymer of acrylic ester or methacrylic ester, or a polymer or a copolymer of acrylic acid or methacrylic acid; a polymer latex of vinyl type such as an ethylene-vinyl acetate copolymer ; a polymer latex of functional group modified type by a monomer

containing functional groups such as a carboxyl group of such polymers; an aqueous adhesive of thermosetting synthetic resin such as an urea resin or a melamine resin; a synthetic resin type adhesive such as polymethyl methacrylate, a polyurethane resin, an unsaturated polyester resin, a vinyl chloride-vinyl acetate copolymer, a polyvinyl butyral or an alkyd resin. These resins may be used alone or in combination as a mixture. Further, known natural or synthetic resin binders may be used alone or in combination as a mixture.

The dry content of binder resin in said porous ink receiving layer is preferably in the range from 0.5 to 30 % by weight, more preferably from 1 to 25 % by weight. The ink- receiving layer preferably comprises from 1 to 10 g/m, more preferably from 2 to 8 glum2 of binder resin. The content of the binder resin is preferably from 1 to 50 parts by weight, more preferably from 2 to 25 parts by weight, per 100 parts by weight of the inorganic pigment particles present in the ink-jet receiving layer.

Said porous ink-receiving layer of the recording material can also contains boric acid or a borate. As the boric acid, not only orthoboric. acid but also metaboric acid and hypoboric acid may be used. As the borate, soluble salts of these boric acids are preferably employed. Specifically, Na2B407-10H20, NaB02-4H20, KOyO, KB02, NH4B409-3H20 and NH4BO2 may, for example, be mentioned.

The dry amount of boric acid or a borate used in said porous ink receiving layer is generally from 5 to 50 % by weight, preferably from 10 to 30 % by weight, as calculated as H3B03 relative to the binder resin. The ink-receiving layer preferably comprises from 0.05 to 5 g/m2, more preferably from 0. 1 to 2 g/m2 of boric acid or borate.

Moreover, said porous ink-receiving layer of the recording material preferably contains at least a surfactant. Preferred examples of surfactants include anionic surfactants, cationic surfactants, amphoteric surfactants, and non-ionic surfactants.

Examples of anionic surfactants comprise an anionic group, such as a carboxyl group, a sulfo group, a phospho group, a sulfuric acid ester group, a phosphoric acid ester group joined to a long chain aliphatic residue. Useful examples of anionic surfactants are, for example, alkylcarboxylates, allcylsulfates, alkylsulfhonates, arallcyl sulfonates, alkylbenzenesulfonates, allcylnaphthalenesulfonates, alkylsulfuric acid esters, alkylphosphoric acid esters, n-acyl-n-allçyltaurines, sulfosuccinic acid esters, sulfoallcylpolyoxyethylene alkylphenyl ether and polyoxyethylene alkylphosphoric acid esters.

Examples of cationic surfactants include 2-vinylpyridine derivatives and poly-4- vinylpyridine derivatives. Examples of amphoteric surfactants include lauryl dimethyl

aminoacetic acid betaine, 2-alkyl-N-carboxymethyl-N-hydroxyethyl imidazolinium betaine, propyldimethylaminoacetic acid betaine, polyoctylpoly-aminoethyl glycine, and imidazoline derivatives.

Useful examples of non-ionic surfactants include non-ionic fluorinated surfactants and non-ionic hydrocarbon surfactants. Examples of non-ionic hydrocarbon surfactants include ethers, such as polyoxyethylene nonyl phenyl ethers, polyoxyethylene octyl phenyl ethers, polyoxyethylene dodecyl phenyl ethers, polyoxyethylene alkyl allyl ethers, polyoxyethylene oleyl ethers, polyoxyethylene lauryl ethers, polyoxyethylene alkyl ethers, polyoxyalkylene alkyl ethers; esters, such as polyoxyethylene oleate, polyoxyethylene distearate, sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxyethylene monooleate, and polyoxyethylene stearate; and glycol surfactants. Specific examples of non-ionic surfactants include octylphenoxy polyethoxy ethanols, such as TritonX-100, X-114, and X-405, available from Union Carbide Co., Danbury, Conn.; acetylenic diols such as 2,4, 7, 9-tetramethyl-5-decyl-4, 7-diol and the like, such as SurfynolTMGA and SurfynolTMCT-136, available from Air Products & Chemicals Co. , Allentown, Pa. , trimethyl nonylpolyethylene-glycol ethers, such as TergitolTMTMN-10 (containing 10 oxyethylene units, believed to be of formula C12H2s0 (C2H40) sH), available from Union Carbide Co. , Danbury, Conn.; non-ionic esters of ethylene oxide, such as MerpolTMSH (believed to be of formula CH3 (CH2) 12 (OC2H4) 80H), available from E. I. Du Pont de Nemours & Co. , Wilmington, Del.; non-ionic esters of ethylene oxide and propylene oxide, such as MerpolTMLFH (believed to be of formula CH3 (CH2) n (OC2H4) 8 (OC3H6) 80H, where n is an integer from about 12 to about 16), available from E. I. Du Pont de Nemours & Co. , Wilmington, Del. , and the like, as well as mixtures thereof. Non-limiting examples of non-ionic fluorinated surfactants include linear perfluorinated polyethoxylated alcohols (e. g., ZonylTMFSN, ZonylTM FSN-100, ZonylFSO, and ZonylTMFSO-100available from DuPont Specialty Chemicals, Wilmington, Del. ), fluorinated alkyl polyoxyethylene ethanols (e. g., FluoradTMFC-170C available from 3M, St. Paul, MN), fluorinated allcyl alkoxylates (e. g., FluoradFC-171 available from 3M, St. Paul, MN), fluorinated alkyl esters (e. g., FluoradTMFC-430, FC-431, and FC-740 available from 3M, St. Paul, MN) and fluorine-substituted alkyl esters and perfluoroalkyl carboxylates (for example, the F-tergentseries manufactured by Neos Co., Ltd. , the Lodyneseries manufactured by Ciba-Geigy, the Monflorseries manufactured by ICI, the Surfluonseries manufactured by Asahi Glass Co. , Ltd. , and the Unidyneseries

manufactured by Daikin Industries, Ltd. ). Preferred nonionic fluorocarbon surfactants include TritonTMX-100, ZonylTMFSO, FluoradTMFC-170C, and FluoradTMFC-171.

The porous ink-receiving layer comprises from 0.01 and 5 g/m2 of said surfactants, preferably from 0.05 and 1 g/m2.

In addition, dispersant agents, thickening agents, pH adjustor agents, lubricants, fluidity modifier agents, surface activators, waterproof agents, mold-releasing agents, whitening agents, ultraviolet absorbing agents, antioxidants, can be added to the porous ink-receiving layer.

The following examples will describe in particular the advantages of the present invention over the prior art.

EXAMPLES Sample 1 (reference). a) Media preparation. A micro-porous ink-jet recording material was obtained by slide coating on a 214g/m2 resin coated paper support a micro-porous layer comprising, as dry coverage per square meters, 40g of DisperalHP14 (an alumina hydrate manufactured by Condea Gmbh, Hamburg, Germany), 4.67g of AirvolTM523 (a polyvinyl alcohol manufactured by Air Products, Allentown, Pennsylvania, having a saponification degree of 88 %, and a polymerization degree of 1,500), 1. 31g of acetic acid, 0.6g of boric acid, 0.16g of TritonTMX-100 (a non-ionic surfactant available from Union Carbide Co. , Danbury, Conn) and 0.029g of ZonylTMFSN-100 (a non-ionic fluorinated surfactant manufactured by DuPont Specialty Chemicals, Wilmington, Del. ). The wet resulting coating was dried and the resulting micro-porous receiving material prepared in roll was converted in A4 samples. b) Print. The A4 sample 1 has been printed and submitted to 7 weeks incubation to check the resistance of the image to air deterioration according to the following procedure.

A solid image pattern including 7 patches (cyan, magenta, yellow, red, green, blue and black patches) was printed on the test sheet by a model Deslcjet 970 ink-jet printer (manufactured by Hewlett-Packard Co. , Palo Alto, California) with the original ink-jet cartridges made by Hewlett-Packard. The reflection density of recorded patches was measured for each single color cyan, magenta, yellow and for each component of the red, green, blue and black area with a densitometer, model TR 1224 (manufactured by Macbeth, a division of Kollmorgen Instrument Corp. , Newburgh, New York). The patch area exhibiting a density near 1.00 was selected for each single color cyan, magenta and yellow; on the other hand, for the red, green and blue composite colors, it was considered each

respective two components to choose the respective density 1.00 area; finally, the three components to choose the respective density 1.00 area were considered for the black composite color. c) Incubation. The sample was submitted to a 2 Klux intensity fluorescent light exposure, at 50% relative humidity and 23°C. The atmosphere air composition was maintained stable during all the test, in particular for the oxygen and H2S, SO2, N02 and 03 gases present in little amounts. The recorded sample surface was maintained free of any physical protection to allow the natural air circulation. After incubation, the density was measured for each selected area in which an initial density near 1.00 had been measured; consequently, the air image resistance could be evaluated. d) Air image resistance evaluation. The evaluation was performed considering the rate of density lost calculated with the formula: Lost rate (%) = [ (DPAi-DU)- (DPm-DUsi)] x 100/ (DPBI-DUBI) in which DPAI = Density of Printed area After Incubation DUAI = Density of Unprinted area After Incubation DPBI = Density of Printed area Before Incubation DPBI = Density of Unprinted area Before Incubation The image resistance of the sample was evaluated by average of the density lost rate for all the 7 colors (cyan, magenta, yellow, red, green, blue and black) : Avg. Lost rate (%) = [C+M+Y+(Mred + Yred)+(Cgreen + Ygreen)+(Cblue + Mblue)+(Cblack + Mblack + Yblack)]1/2 with C = lost rate % of Cyan M = lost rate % of Magenta Y = lost rate % of Yellow Mred = lost rate % of Magenta component in red area Yred = lost rate % of Yellow component in red area Cgreen = lost rate % of Cyan component in green area Ygreen = lost rate % of Yellow component in green area Cblue= lost rate % of Cyan component in blue area Mb ; ue= lost rate % of Magenta component in blue area Cblack = lost rate % of Cyan component in black area Mbiack = lost rate % of Magenta component in black area

Yblack= lost rate % of Yellow component in black area The optical density lost percentage data obtained from the procedure described above determine the air color fading of the ink-jet recording material.

Sample 2 (invention) was prepared as Sample 1, excepted that the microporous material was submitted to an additional printing step, before the step b, using an additional cartridge containing the aqueous solution Al comprising the compound (1) used in the present invention at a concentration of 0.5 % by weight, sulfuric acid at a concentration of 0.086 % by weight and 1,5 pentandiol as humectant at a concentration of 16 % by weight.

Sample 3 (invention) was prepared as Sample 2, but the additional cartridge contained the aqueous solution A2 comprising the compound (1) used in the present invention at a concentration of 1.0 % by weight, sulfuric acid at a concentration of 0.171 % by weight and 1,5 pentandiol as humectant at a concentration of 16 % by weight.

Sample 4 (invention) was prepared as Sample 2, but the additional cartridge contained the aqueous solution A3 comprising the compound (1) used in the present invention at a concentration of 2.0 % by weight, sulfuric acid at a concentration of 0.342 % by weight and 1,5 pentandiol as humectant at a concentration of 16 % by weight.

The results are reported in table 1.

Table 1 Samples Compound (1) 1,5 pentandiol Sulfuric acid % Ave OD lost % Ave OD lost Print quality % in solution % in solution % in solution after 7 weeks after 13 weeks Sample 1----14. 9-32.7 OK (Reference) Sample 2 0.5 16 0.086-11. 2-19.8 OK (invention) Sample 3 1.0 16 0.171-10. 2-18.5 OK (invention) Sample 4 2.0 16 0.342-7. 8-14.3 OK (Invention) Table 1 clearly shows that the reference Sample 1, with no additives, presented a serious deterioration of the color after 7 incubation weeks only. On the contrary, Samples 2 to 4, comprising the compound (1) used in the present invention at different concentrations, showed a moderate average lost in density.