WO2005032836A1

WO2005032836A1 - Recording medium

Info

Publication number: WO2005032836A1
Application number: PCT/NL2004/000693
Authority: WO
Inventors: Sebastianus Gerardus Johannes Maria Kluijtmans; Akira Kase
Original assignee: Fuji Photo Film B.V.
Priority date: 2003-10-03
Filing date: 2004-10-04
Publication date: 2005-04-14

Abstract

The present invention relates to a recording medium, in particular an ink-jet recording medium of photographic quality that has improved lightfastness. According to the present invention an ink-jet recording medium is provided, comprising a support to which at least an underlayer and an overlayer is supplied in which a layer comprising acid processed gelatin is located between said layers and wherein the overlayer contains at least one type of modified gelatin. The present invention is further directed to methods for obtaining and using such a medium.

Description

Title: Recording medium

Field of the invention The present invention relates generally to a recording medium, in particular an ink -jet recording medium of photographic quality having a good image printing quality, in particular a good lightfastness, as well as to methods for preparing such media.

Background of the invention In a typical ink-jet recording or printing system, ink droplets are ejected from a nozzle at high speed towards a recording element or medium to produce an image on the medium. The ink droplets, or recording liquid, generally comprise a recording agent, such as a dye, and a relatively large amount of solvent in order to prevent clogging of the nozzle. The solvent, or carrier liquid, typically is based on water, and further comprises organic material such as monohydric alcohols and the like. An image recorded as liquid droplets requires a receptor on which the recording liquid dries quickly without running or spreading. High quality image reproduction using ink -jet printing techniques requires receptor substrates, typically sheets of paper or opaque or transparent film, that readily absorb ink droplets while preventing droplet diffusion or migration. Good absorption of ink encourages image drying while minimizing dye migration by which good sharpness of the recorded image is obtained. One of the important properties of an ink -jet receptive coating formulation is the liquid absorptivity. The majority, if not all, of the ink solvent has to be absorbed by the coating layer itself. Only when paper or cloth or cellulose is used as a support, some part of the solvent may be absorbed by the support. It is thus clear that both the water soluble polymer and the filler should have a significant ability to absorb the ink solvent. US-A-2002/142141 discloses an image -receiving layer, which contains at least one water soluble polymer like polyvinyl alcohol, that swells when ink-jet ink is attached to the image-receiving layer. Improved performance with respect to durability, scuff resistance and image fidelity is said to be obtained. In EP-A-875 393 a sheet for ink-jet recording is disclosed in which micro porous polysaccharide particles are provided in an ink -receiving layer comprising for example polyvinyl alcohol. The micro porous particles are said to give very good ink receptivity and also to provide good sheet feeding property in ink -jet printers. DE-A-223 48 23 and US-A-4 379 804 disclose methods in which gelatin is used in ink-receiving layers of ink-jet receiving sheets. From these documents, it has become clear that gelatin has an advantageous function for the absorption of ink solvents. The gelatin is said to improve smudge resistance, increase the definition quality, give high gloss, fast water absorbing properties, easy to achieve high water resistance and good dye fading resistance. There are at least two major disadvantages to a gelatin-based coating, which are not much addressed in the existing art. These disadvantages include curl and brittleness of the coating. Various countermeasures have been suggested to overcome these problems. In WO-A-00/53406 the use of at least one plasticizer selected from the group comprising 2-pyrrolidone and its derivatives, or urea and its derivatives is described to overcome the curl and brittleness of this type coating. Besides the curl and brittleness, other problems are encountered using ink receiving layers based on gelatin or gelatin mixtures with water soluble polymers. These are problems like beading, bleed and matte appearance at high densities. To overcome these problems various solutions have been proposed. US-A-6 183 844 describes the use of highly filled multilayers to improve bleed and wet smear resistance. EP-A-0 742 109 describes the use of a combination of anionic and cationic fluorine containing surfactants in a gelatin containing ink receiving layer in order to improve dot reproduction especially for graphic art applications. EP-A-1 080 936 describes the use of a non-ionic surfactant giving a lower surface tension in the layer of an ink receptive multilayer farthest from the support and a second non ionic surfactant giving a higher surface tension in the layer nearer to the support material. Improved gloss and bleed is claimed. WO 00/53406 describes one- and two-layer constructions comprising an acid processed gelatin and a plasticizer for which a good curl stability, flexibility, fast drying and good dye fading properties are claimed. A further important property of inkjet media is that they should provide for a good lightfastness, υiz. the printed images must not fade over longer periods of time. In order to improve the lightfastness of inkjet media, several approaches have been suggested in the prior art. JP-A-4 201 594, for instance, proposes to include hyperfine powder of transition metal oxides in the ink accepting layer and GB-A-2 147 003 suggests to combine metal salts with cationic polymeric substances to improve lightfastness of the produced images. Furthermore, JP-A-2002/220 559 and EP-A-0 869 010 describe a specific copolymer, which is to be included in one or more of the layers of the inkjet media, to improve lightfastness. Although some improvement can be obtained by the described methods there remains a need for ink -jet material with good lightfastness. At the same time this inkjet material should provide for good image printing quality, good drying properties, improved curl and brittleness, having at the same time good behaviour on bleed, beading and matte appearance at high density parts and also be available at low cost. It is towards fulfilling this need that the present invention is directed.

Summary of the invention The object of the present invention is to provide a recording medium having good overall properties, said recording medium more in particular being suited to produce images of photographic quality, wherein said medium has an improved lightfastness. At the same time, it desirable that the media of the present invention maintain other favorable properties with respect to brittleness at low humidities, curl behaviour, beading, matte appearance at high densities and bleeding properties. It has been found that these objectives can be met by providing a recording medium comprising a support and an ink receiving layer adhered to said support, where the ink receiving layer is a multilayer comprising at least one underlayer and one overlayer and wherein an intermediate layer comprising acid processed gelatin is located in between said overlayer and said underlayer(s). Detailed description The invention is directed to a recording medium comprising a support and an ink-receiving layer adhered to said support, wherein the ink receiving layer is a multilayer comprising at least one overlayer comprising at least one type of modified gelatin, at least one underlayer, and an intermediate layer comprising an acid processed gelatin is located between said overlayer and said underlayer. This intermediate layer may comprise other ingredients as is described below for the underlayer. The underlayer is a layer that is closer to the support than the overlayer. The overlayer in the medium of the present invention is generally the toplayer, υiz. the layer that is furthest away from the support and that is contacted first with the ink upon printing. It is possible to provide a further layer on the overlayer, which further layer then becomes the toplayer. In this case the overlayer is a multilayer of sublayers. Alsp the. underlayer of this invention may be a multilayer of sublayers. The total number of sublayers is not particularly limited and depends largely on the available technique for application of layers and the required ink receiving properties of the ink receiving layer. The total number of sublayers may be from 2 to 25, more preferably from 3 to 17. The present inventors have found that by providing an inkjet recording medium having a layer comprising acid processed gelatin in between the overlayer and the underlayer of the ink receiving layer, unexpected improvements with respect to lightfastness of the medium are obtained. Lightfastness may be assessed e.g. by exposing for 144 hrs a sample to xenon light (85 000 lx) in an Atlas Wether-O-Meter C I 35A, (manufactured by Atlas (Illinois, U.S.A.)) and measuring the image density of the color on the printed area before and after the xenon exposure using a reflection densitometer (X- Rite 310TR). Without wishing to be bound by theory, it is assumed that the improvements obtained according to the present invention are due to the fact that the pH of ink is usually lower than 7 (except for magenta ink, which usually has a pH that is between 7 and 8). As a result, during image printing, the ink may be "captured" in a suitable layer in accordance with the present invention. Preferably this layer, is the layer directly under (υiz. in contact with) the overlayer. When this layer comprises an acid processed gelatin this layer might act as a mordant, stabilizing the dyes when applied to the medium. By result the acid processed gelatin thus fixes the dye. The overlayer comprises preferably a modified gelatin with an IEP which is in general lower, than the IEP of the acid processed gelatin. Preferably the difference in IEP between the modified gelatin in the overlayer and acid processed gelatin in the intermediate layer is at least 1, more preferably at least 2. The ink will pass the top layer without any difficulty. Consequently, once passed the overlayer, the dye will be captured and stabilised in the underlayer and not diffuse from the, underlayer to other layers, which results in better color density and improved lightfastness. According to a preferred embodiment, the acid processed gelatin is selected from the group of acid processed bone, skin, cow or pig (modified) gelatin and preferably has an IEP from 6.0 to 11. The acid processed gelatin used in the intermediate layer in between the overlayer and the underlayer may be applied in an amount of 0.1 to 10 g/m², more preferably from 0.2 to 5.0 g/m² and most preferably from 0.5 to 3 g/m². The layer comprising the acid processed gelatin may further comprise thickener agents, biocides, crosslinking agents and further various conventional additives such as colorants, colored pigments, pigment dispersants, mold lubricants, permeating agents, fixing agents for ink dyes, UV absorbers, anti-oxidants, dispersing agents, anti-foaming agents, leveling agents, fluidity improving agents, antiseptic agents, brightening agents, viscosity stabilizing and/or enhancing agents, pH adjusting agents, anti- mildew agents, anti-fungal agents, agents for moisture-proofing, agents for increasing the stiffness of wet paper, agents for increasing the stiffness of dry paper and anti-static agents. The above-mentioned various additives can be added ordinarily in an amount, such that the total additives content ranges of from 0 to 10 weight % based on the solid content of this layer composition. The overlayer of this invention comprises a modified gelatin, and may further comprise water insoluble particles inter alia to regulate the slip behaviour and optionally one or more water soluble polymers, surfactants and other additives to optimise the surface properties. The term "modified gelatin" as used herein, refers to gelatin compounds in which at least part of the NH2 groups is chemically modified. A variety of modified gelatins can be used in the overlayer. Good results (i.e. in particular good gloss) are obtained, when at least 30% of the NH₂ groups of the gelatin is modified by a condensation reaction with a compound having at least one carboxylic group as described among others in DE-A-19721238. The compound having at least one carboxylic group can have an other functional group like a second carboxylic group and a long aliphatic tail, which in principle is not modified. Long tail in this context means from at least 5 to as much as 25 C atoms. This aliphatic chain can be modified still to adjust the properties like water solubility and ink receptivity. Preferred modified gelatins comprise an alkyl group (more preferably a Cs-C25-alkyl group), a fatty acid group (more preferably C5-C₂5-fatty acid group), or both. Even more preferably the gelatins comprise a Cγ-Cis-alkyl group, a C7-Cιβ-fatty acid group, or both. Especially preferred gelatins of this type are succinic acid modified gelatins in which the succinic acid moiety contains an aliphatic chain from at least 5 to 25 carbon-atoms, where the chain can still be modified to a certain extend to adjust the water soluble properties or ink receptive properties. Most preferred is the use of dodecenylsuccinic acid modified gelatin, in which at least 30% of the NH2 groups of the gelatin have been modified with said dodecenylsuccinic acid. Another method for obtaining modified gelatin is described in EP-A-

0576911, where said gelatin is formed from gelatin containing pendant amine groups and pendant carboxylic groups wherein at least one amine group of said gelatin is modified to form an amide of the formula -NHCOR. The process typically involves reaction of an amine group with an activated carboxyl, i.e. a reaction product of a carboxyl activating agent and carboxylic acid, i.e., RCOOH wherein R represents substituted or unsubstituted alkyl of 1-10 carbons, substituted or unsubstituted aryl of 6-14 carbons, or substituted or unsubstituted arylalkyl of 7-20 carbons. Other suitable methods are described by V.N. Izmailova, et al. (Colloid Journal, vol. 64, No. 5, 2002, page 640-642), and by O. Toledano, et al. (Journal of Colloid and Interface Science 200, page 235-240) wherein hydrophobic groups are attached to gelatin molecules by reacting gelatin with respectively N-hydroxysuccinimide ester of caprylic acid and N-hydroxysuccinimide ester of various fatty acids (C4-C16). Other modified gelatins giving good results are gelatins modified to have quaternary ammonium groups. An example of such a gelatin is the "Croquat™" gelatin produced by Croda Colloids Ltd. Still another modified gelatin known in the common gelatin technology, such as phtalated gelatin and acetylated gelatins are also suitable to be used in this invention. The modified gelatin can be used alone or in combination with another water soluble polymer. Examples of these polymers include: fully hydrolysed or partially hydrolysed polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, hydroxypropyl cellulose, polyvinylpyrolidone, any gelatin whether lime- processed or acid processed made from animal collagen, preferably gelatin made from pig skin, cow skin, pig bone o cow bone, polyethylene oxide (PEO), polyacrylamide, and the like. Preferably polyethylene oxide or polyvinylpyrollidone having a molecular weight of between 30 000 and 600 000, preferably between 50 000 and 400 000 is used. The modified gelatin is applied in the overlayer preferably in an amount ranging from 0.3 to 5 g/m² and most preferably from 0.5 to 3 g/m². A suitable amount of the water soluble polymer in the mixture is varying between 0 and 75 wt% of the amount of the modified gelatin. In case said water soluble polymer amount is higher than 75wt%, the advantages of the modified gelatin may become less pronounced. The mere application of the modified gelatin or mix of modified gelatin and water soluble polymers improves the characteristics with respect to drying and finger smearing properties. A further improvement of above mentioned properties can be obtained by including in the overlayer a fluorosurfactant in the amount between 2.5 mg/m² and 250 mg/m². It was found that this kind of surfactants improves amongst others the gloss and beading. Beading is defined as the phenomenon that large ink dots become visible on the printed image. The mechanism of "beading" is not clear yet. One hypothesis is that several small ink drops coalesce with each other on the surface of the ink jet media and form large ink droplets. The term "fluorosurfactant" as used herein, refers to surfactants (viz. molecules having a hydrophilic and a hydrophobic part) that contain fluorocarbon or a combination of fluorocarbon and hydrocarbon as the hydrophobic part. Suitable fluorosurfactants may be anionic, non-ionic or cationic. Examples of suitable fluorosurfactants are: fluoro C2-C20 alky Icarboxy lie acids and salts thereof, disodium N-perfluorooctanesulfonyl glutamate, sodium 3-(fluoro-C6-Cn alkyloxy)-l-C3-C₄ alkyl sulfonates, sodium 3-(omega -fluoro-Cβ-Cs alkanoyl-N-ethylamino)-l-propane sulfonates, N-[3- (perfluorooctanesulfonamide)-propyl]-N,N-dimethyl-N-carboxymethylene ammonium betaine, perfluoro alkyl carboxylic acids (e.g. C7-C13 alkyl carboxylic acids) and salts thereof, perfluorooctane sulfonic acid diethanolamide, Li, K and Na perfluoro C4-C12 alkyl sulfonates, Li, K and Na N-perfluoro C4-C13 alkane sulfonyl — N- alkyl glycine, fluorosurfactants commercially available under the name Zonyl^® (produced by E.I. Du Pont) that have the chemical structure of fCH2CH2SCH CH2Cθ Li or R_fCH2CH2θ(CH₂CH2θ)_x H wherein R_f = F(CF₂CF₂)₃-8 and x = 0 to 25, N- propyl-N-(2-hydroxyethyl)perfluorooctane sulfonamide, 2-sulfo-l,4- bis(fluoroalkyl)butanedioate, 1,4-bis (fluoroalkyl)-2-[2-N,N,N- trialkylammonium) alkyl amino] butanedioate, perfluoro Ce-Cio alkylsulfonamide propyl sulfonyl glycinates, bis-(N-perfluorooctylsulfonyl-N- ethanolaminoethyl)phosphonate, mono-perfluoro CG-CI6 alkyl-ethyl phosphonates, and perfluoroalkylbetaine. Also useful are the fluorocarbon surfactants described e.g. in US-A-4 781 985 and in US-A-5 084 340. Preferably the fluorosurfactant is chosen from Li, K and Na N-perfluoro C4-C13 alkane sulfonyl — N- alkyl glycine, 2-sulfo-l,4-bis(fLuoroalkyl)butanedioate, 1,4-bis (fluoroalkyl)-2-[2-(N,N,N- trialkylammonium alkyl amino] butanedioate, perfluoro alkyl subsitituted carboxylic acids commercially available under the name Lodyne^® (produced by Ciba Specialty Chemicals Corp.) and fluorosurfactants commercially available under the name Zonyl^® (produced by E.I. Du Pont) that have the chemical structure of RfCH CH₂SCH₂CH2C02Li or fCH₂CH2θ(CH2CH₂O)_x H wherein R_f = F(CF₂CF₂)3-8 and x = 0 to 25. Beside the modified gelatin or modified gelatin/water soluble polymer mixture and fluorosurfactant it may be desirable to add in the overlayer an anti-blocking agent to prevent image transfer when several printed inkjet mediums are piled up. Very suitable anti-blocking agents (also known as matting agents) have a particle size from 1 to 20 μm, preferably between 2 and 10 μm. The amount of matting agent is from 0.01 to 1 g/m², preferably from 0.02 to 0.5 g/m². The matting agent can be defined as particles of inorganic or organic materials capable of being dispersed in a hydrophilic organic colloid. The inorganic matting agents include oxides such as silicon oxide, titanium oxide, magnesium oxide and aluminium oxide, alkali earth metal salts such as barium sulphate, calcium carbonate, and magnesium sulphate, and glass particles. Besides these substances one may select inorganic matting agents which are disclosed in West German Patent No. 2,529,321, British Patent Nos. 760,775 and 1,260,772, U.S. Pat. Nos.

1,201,905, 2,192,241, 3,053,662, 3,062,649, 3,257,296, 3,322,555, 3,353,958, 3,370,951, 3,411,907, 3,437,484, 3,.523,022, 3,615,554, 3,635,714, 3,769,020, 4,021,245 and 4,029,504. The organic matting agents include starch, cellulose esters such as cellulose acetate propionate, cellulose ethers such as ethyl cellulose, and synthetic resins. The synthetic resins are water insoluble or sparingly soluble polymers which include a polymer of an alkyl(meth) aery late, an alkoxy alky l(meth) aery late, a glycidyl(meth) aery late, a (meth)acrylamide, a vinyl ester such as vinyl acetate, acrylonitrile, an olefin such as ethylene, or styrene and a copolymer of the above described monomer with other monomers such as acrylic acid, methacrylic acid, alpha, beta -unsaturated dicarboxylic acid, hy droxy alkyl (meth) aery late, sulfoalkyl(meth)acrylate and styrene sulfonic acid. Further, a benzoguanamin-formaldehyde resin, an epoxy resin, nyl n, polycarbonates, phenol resins, polyvinyl carbazol or polyvinylidene chloride can be used. Besides the above are used organic matting agents which are disclosed in British Patent No. 1,055,713, U.S. Pat. Nos. 1,939,213,

2,221,873, 2,268,662, 2,322,037, 2,376,005, 2,391,181, 2,701,245, 2,992,101, 3,079,257, 3,262,782, 3,443,946, 3, 516,832, 3,539,344,554, 3,591,379, 3,754,924 and 3,767,448, Japanese Patent O.P.I. Publication Nos. 49- 106821/1974 and 57-14835/1982. These matting agents may be used alone or in combination. In another embodiment of this invention the beneficial effects of the modified gelatin and the fluorosurfactant is generated by applying these compounds in a separate overlayer coating, meaning, that also the overlayer is a multilayer. In this case it is preferable to have the fluorosurfactant in a coating layer farthest away from the substrate and the modified gelatin applied under this coating layer. The overlayer may optionally include thickener agents, biocides crosslinking agents and further various conventional additives such as colorants, colored pigments, pigment dispersants, mold lubricants, permeating agents, fixing agents for ink dyes, UV absorbers, anti-oxidants, light stabilising agents, dispersing agents, anti-foaming agents, leveling agents, fluidity improving agents, antiseptic agents, brightening agents, viscosity stabilizing and/or enhancing agents, pH adjusting agents, anti-mildew agents, anti-fungal agents, agents for moisture-proofing, agents for increasing the stiffness of wet paper, agents for increasing the stiffness of dry paper and antistatic agents. The above-mentioned various additives can be added ordinarily in a range of 0 to 10 weight % based on the solid content of the ink receiving layer composition. Also the underlayer can be a multilayer of sublayers. It was found that in case the underlayer is a multilayer it is beneficial to apply different concentrations of gelatin and water soluble polymer in the sublayers of the underlayer. A lower concentration of gelatin and water soluble polymer in the sublayer closest to the support enables a lower viscosity of the mixture which improves the coatability and allows higher coating speeds. In a specific embodiment an adhesion promoting layer is applied between the support and the underlayer to enhance the adhesion of the coated layers onto the support. This adhesion promoting layer may be coated in a separate step or simultaneously with the receiving layers. The underlayer preferably comprises gelatin and a hydrophilic polymer and optionally additives to adjust the physical properties. There is a variety of gelatins, both non-modified as well as modified gelatins which can be used in the underlayer. Examples of non-modified gelatins are alkali-treated gelatin (cattle bone or hide gelatin), acid-treated gelatin (pigskin, cattle/pig bone gelatin), recombinant gelatin or hydrolyzed gelatin. Examples of modified gelatins are acetylated gelatin, phthalated gelatin, quaternary ammonium modified gelatin, et cetera. These gelatins can be used singly or in combination for forming the underlayer. Acid and alkali treated gelatins are preferred. Water soluble polymers suitable to be mixed with the

(modified)gelatin of the underlayer and the intermediate layer include polyvinyl alcohol- (PVA-)based polymers, such as fully hydrolysed or partially hydrolysed polyvinyl alcohol (PVA), carboxylated polyvinyl alcohol, copolymers and terpolymers of PVA with other polymers, water soluble cellulose derivatives such as hydroxyethyl cellulose, methyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, casein, gum arabic, polyacrylic acid and its copolymers or terpolymers, polymethylacrylic acid and its copolymers or terpolymers, and any other polymers, which contain monomers of carboxylic acids such as acrylic acid, methacrylic acid, maleic acid and crotonic acid, polyvinylpyrolidone (PVP), polyethylene oxide, polyacrylamide, 2-pyrrolidone and its derivatives such as N (2-hydroxyethyl)-2-pyrrolidone and N-cyclohexyl- 2-pyrrolidone, urea and its derivatives such as imidazolidinyl urea, diazolidinyl urea, 2-hydroxyethylethylene urea, and ethylene urea. There are water soluble polymers which have very limited compatibility with gelatin. These polymers include fully hydrolyzed or partially hydrolyzed polyvinyl alcohol, hydroxyethyl cellulose, methyl cellulose, hydroxypropyl cellulose, polyethylene oxide, polyacrylamide, and the like. When a solution of gelatin in water is mixed with a solution in water of one of the above described polymers, micro or macro phase separation occurs in solution which persists in the dried coating. The dried coating exhibits high haze, low transparency, and low gloss. The system of a mixture of gelatin and a water soluble polymer is very well illustrated by means of a gelatin/PEO mixture as example. A homogeneous gelatin PEO mixture, i.e. a mixture where no phase separation occurs, may be obtained by adjusting the pH of the mixture. However there is no unique rule to determine the pH at which there is no phase separation. The best way is to follow the practical approach by making the required mixture of gelatin and water soluble polymer in water and adding alkali or acid until a homogeneous solution is obtained. The suitable pH range mainly depends on the gelatin type used and type of the water soluble polymer. It was found that (modified) acid treated gelatins having an iso-electric-point (IEP) of between 6.0 and 11 give a homogeneous solution with PEO at a pH below 5. At pH between 5 and 10, the mixture remains turbid, which indicate that the mixture is not homogeneous. At a pH higher than 11, a homogeneous solution can be obtained. For a lime treated gelatin, that has IEP value of between 4 and 6.0, a homogeneous mixture between gelatin and PEO can be obtained at a broader pH ranges, i.e. at a pH value lower than 4.5 or at a pH value higher than 6.0. In addition to the above mentioned pH adjustment, we have found, that it is not only important to have a homogeneous solution, but it is also beneficial to have a molecular weight of PEO of at least 100 000. A lower MW might also give satisfactory results, but in general most of the important properties, like curling, drying speed and brittleness improve when using a high MW PEO. In addition to this, it appeared to be beneficial to use an underlayer comprising various layers, in which the various layers have a different gelatin/PEO ratio. We have found that a low gelatin/PEO ratio in the layer nearest to the overlayer and a higher gelatin/PEO ratio at the layers nearer to the support have a beneficial effect on properties like bleeding and beading. More specifically gelatin/PEO ratio's (wt./wt.) in the layer nearest to the overlayer preferably vary between 1/1 to 8/1 and the gelatin/PEO ratios (wt./wt.) in the layers nearest to the support should vary between 1/1 and 12/1 with the condition, that the gelatin/PEO ratio of the layer nearest to the overlayer is always lower, than the ratio of the other gelatin-PEO layers. When using more gelatin-PEO layers in the underlayer it is further beneficial to use a gradient for the gelatin/PEO ratio, meaning, that the gelatin/PEO ratio is lowest in the layer adjacent to the overlayer and said ratio is highest for the layer most near to the substrate. The homogeneous gelatin-PEO solution of the underlayer, which is supplied to the substrate has a gelatin concentration between 5 and 20 wt.%. Embodiments using PEO are described; similar embodiments can be described for other mixtures of gelatin and water soluble polymers having a limited compatibility with each other. It has been found by the present inventors that one may substitute the PEO with other water soluble polymers mentioned above such as PVP or PVA or a mixture between two or more water soluble polymers such as PEO and PVP. The ratio between the gelatin and said water soluble polymer(s) should be in the same ranges as it is described above for gelatin-PEO system. Good results are obtained with PVA-based polymers. In general a large variety of PVA-based polymers can be used, but the preferred PVA-based polymers are those which have been modified to give a good miscibility with aqueous gelatin solutions. These modifications are such, that in the PVA-based polymer back bone groups are introduced which provide a hydrogen bonding site, an ionic bonding site, carboxylic groups, sulfonyl groups, amide groups and the like, thus providing a modified PVA-based polymer. A modified PVA- based polymer giving very good results is a poly(vinyl alcohol) -co-poly (n-vinyl formamide) copolymer (PVA-NVF). Very suitable PVA-NVF copolymers for use with the present invention are the copolymers described in WO-A-03/054029, which have the general formula I:

wherein n is between 0 and about 20 mole percent; m is between about 50 and about 97 mole percent; x is between 0 and about 20 mole percent; y is between 0 and about 20 mole percent; z is between 0 and about 2 mole percent and x+y is between about 3 and about 20 mole percent; Ri, and R3 are independently H, 3-propionic acid or Ci-Ce alkyl ester thereof, or is 2-methyl-3-propionic acid or Ci-Cβ alkyl ester thereof; and R2 and R4 are independently H or Ci-Ce alkyl. The water soluble polymer (or mixture of water soluble polymers) is preferably applied for the underlayer and/or the intermediate layer in an amount ranging from 0.5 to 15 g/m², more preferably from 1.0 to 8.0 g/m². The homogeneous aqueous solution of the underlayer or the intermediate layer may further contain the following ingredients in order to improve the ink receiving layer properties with respect to ink receptivity and strength: - One or more plasticizers, such as ethylene glycol, diethylene glycol, propylene glycol, polyethylene glycol, glycerol monomethylether, glycerol monochlorohydrin, ethylene carbonate, propylene carbonate, tetrachlorophthalic anhydride, tetrabromophthalic anhydride, urea phosphate, triphenylphosphate, glycerolmonostearate, propylene glycol monostearate, tetramethylene sulfone, N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, and polymer lattices with low Tg-value such as polyethylacrylate, polymethylacrylate and the like. - One or more fillers; both organic and inorganic particles can be used as fillers. Useful filler examples are represented by silica (colloidal silica), alumina or alumina hydrate (aluminazol, colloidal alumina, a cat ion aluminum oxide or its hydrate and pseudo-boehmite), a surface-processed cat ion colloidal silica, aluminum silicate, magnesium silicate, magnesium carbonate, titanium dioxide, zinc oxide, calcium carbonate, kaolin, talc, clay, zinc carbonate, satin white, diatomaceous earth, synthetic amorphous silica, aluminum hydroxide, lithopone, zeolite, magnesium hydroxide and synthetic mica. Useful examples of organic fillers are represented by polystyrene, polymethacrylate, polymethyl-methacrylate, elastomers, ethylene-vinyl acetate copolymers, polyesters, polyester-copolymers, poly aery late s, polyvinylethers, polyamides, polyolefins, polysilicones, guanamine resins, polytetrafluoroethylene, elastomeric styrene-butadiene rubber (SBR), urea resins, urea-formalin resins. Such organic and inorganic fillers may be used alone or in combination. - One or more mordants. Mordants may be incorporated in the ink- receptive layer of the present invention. Such mordants are represented by cationic compounds, monomeric or polymeric, capable of complexing with the dyes used in the ink compositions. Useful examples of such mordants include quaternary ammonium block copolymers. Other suitable mordants comprise diamino alkanes, ammonium quaternary salts and quaternary acrylic copolymer latexes. Other suitable mordants are fluoro compounds, such as tetra ammonium fluoride hydrate, 2,2,2-trifLuoroethylamine hydrochloride, 1- (alpha, alpha, alpha -trifluoro-m-tolyl) piperazine hydrochloride, 4-bromo- alpha, alpha, alpha -trifluoro-o-toluidine hydrochloride, difluorophenylhydrazine hydrochloride, 4-fluorobenzylamine hydrochloride, 4- fluoro- alpha, alpha -dimethylphenethylamine hydrochloride, 2- fluoroethylamine hydrochloride, 2-fluoro- 1-methyl pyridinium-toluene sulfonate, 4-fluorophenethylamine hydrochloride, fluorophenylhydrazine hydrochloride, l-(2-fluorophenyl) piperazine monohydrochloride, 1 -fluoro pyridinium trifluoromethane sulfonate. - One or more conventional additives, such as: • pigments: white pigments such as titanium oxide, zinc oxide, talc, calcium carbonate and the like; blue pigments or dyes such as cobalt blue, ultramarine or phthalocyanine blue; magenta pigments or dyes such as cobalt violet, fast violet or manganese violet; biocides; pH controllers; preservatives; viscosity modifiers; • dispersing agents; UV absorbing agents; brightening agents; anti-oxidants; light stabilizing agents • antistatic agents; and/or anionic, cationic, non-ionic, and/or amphoteric surfactants, typically used in amounts ranging from 0.1 to 1000 mg/m², preferably from 0.5 to 100 mg/m². These additives may be selected from known compounds and materials in accordance with the objects to be achieved. The above-mentioned additives (plasticizers, fillers/pigments, mordants, conventional additives) may be added in a range of 0 to 30% by weight, based on the solid content of the water soluble polymers and / or gelatin in the underlayer or the intermediate layer. The particle sizes of the non water-soluble particulate additives should not be too high, since otherwise a negative influence on the resulting surface will be obtained. The used particle size should therefore preferably be less than 10 μm, more preferably 7 μm or less. The particle size is preferably above 0.1 μm, more preferably about 1 μm or more for handling purposes. The gelatin is preferably used in a total amount of from 1 to 30 g/m², and more preferably from 2 to 20 g/m². The amount of hydrophilic polymer is typically in the range from 100 mg/m² to 30 g/m² and more preferably between 200 mg/m² and 20 g/m². When preparing the ink -jet-receiving sheet by coating a plurality of layers, each layer comprises an amount of gelatin ranging from 0.5 to 10 g/m². If desired, the gelatin can be cross-linked in the image-recording elements of the present invention in order to impart mechanical strength to the layer. This can be done by any cross-linking agent known in the art. For gelatin, there is a large number of known cross-linking agents- also known as hardening agents. Examples of the hardener include aldehyde compounds such as formaldehyde and glutar aldehyde, ketone compounds such as diacetyl and chloropentanedion, bis (2-chloroethylurea), 2-hydroxy-4, 6- dichloro-l,3,5-triazine, reactive halogen-containing compounds disclosed in US-A-3 288 775, carbamoyl pyridinium compounds in which the pyridine ring carries a sulphate or an alkyl sulphate group disclosed in US-A-4 063 952 and US-A-5 529 892, divinylsulfones, and the like. These hardeners can be used singly or in combination. The amount of hardener used, preferably ranges from 0.1 to 10 g, and more preferably from 0.1 to 7 g based on 100 g of gelatin contained in the ink-receiving layer. For PVA, for example, it is preferable to choose a cross-linking agent selected from borax, glyoxal, dicarboxylic acids and the like. . The process for preparing a recording medium according the invention comprises the steps of: providing at least a first, a second and a third solution, the first solution comprising the modified gelatin for the overlayer of said medium, the second solution comprising the (modified) acid processed gelatin for the intermediate layer, and the third solution for the underlayer, followed by a step wherein said solutions are applied consecutively or simultaneously to a substrate to provide a medium having at least: one overlayer comprising the gelatin from the first solution, at least one underlayer comprising the third solution and one intermediate layer located in between said overlayer and said underlayer comprising the second solution, followed by drying the coated support. The coating method can be any method known in the art and is for example, a curtain coating, an extrusion coating, an air-knife coating, a slide coating, a roll coating method, reverse roll coating, dip coating processes and a rod bar coating. The support used in this invention may suitably be selected from a paper, a photographic base paper, a paper coated on one or both sides with a polymer layer, pigment coated paper, a synthetic paper or a plastic film in which the top and back coatings are balanced in order to minimise the curl behaviour. The backside coating comprises gelatin or a water soluble polymer in an amount ranging preferably from 1 to 20 g/m², more preferably from 4 to 15 g/m². The optimum amount of the backside coating depends on the type of gelatin, the type of water soluble polymer and on the composition of the layers at the ink receiving side of the medium and is determined experimentally. The preferred polymer for the backside coating is gelatin. An important characteristic of the inkjet recording medium is the gloss. It has been found that the gloss of the medium can be improved by selecting the appropriate surface roughness of the used support. It was found, that providing a support having a surface roughness characterised by the value Ra being less than 1.0 μm, preferably below 0.8 μm a very glossy medium can be obtained. A low value of the Ra indicates a smooth surface. The Ra is measured according to DIN 4776; software package version 1.62 with the following settings:

(1) Point density 500 P/mm (2) Area 5.6 x 4.0 mm² (3) Cut-off wavelength 0.80 mm (4) Speed 0.5 mm/sec, using a UBM equipment. The base paper to be used as the support for the present invention is selected from materials conventionally used in high quality printing paper. Generally it is based on natural wood pulp and if desired, a filler such as talc, calcium carbonate, TiO₂, BaSO4, and the like can be added. Generally the paper also contains internal sizing agents, such as alkyl ketene di er, higher fatty acids, paraffin wax, alkenylsuccinic acid, epichlorhydrin fatty acid amid and the like. Further the paper may contain wet and dry strength agents such as a polyamine, a poly-amide, polyacrylamide, poly-epichlorhydrin or starch and the like. Further additives in the paper can be fixing agents, such as aluminium sulphate, starch, cationic polymers and the like. The Ra value for a normal grade base paper is well above 1.0 μm typically above 1.3 μm. In order to obtain a base paper with a Ra value below 1.0 μm such a normal grade base paper can be coated with a pigment. Any pigment can be used. Examples of pigments are calcium-carbonate, Tiθ2, BaS0₄, clay, such as kaolin, styrene- acr lic copolymer, Mg-Al-silicate, and the like or combinations thereof. The amount being between 0.5 and 35.0 g/m² more preferably between 0.5 and 20.0 g/m². This pigmented coating can be applied as a pigment slurry in water together with a suitable binders like styrene-butadiene latex, methyl methacrylate-butadiene latex, polyvinyl alcohol, modified starch, polyacrylate latex or combinations thereof, by any technique known in the art, like dip coating, roll coating, blade coating or bar coating. The pigment coated base paper may optionally be calendered. The surface roughness can be influenced by the kind of pigment used and by a combination of pigment and calendering. The base pigment coated paper substrate has preferably a surface roughness between 0.4 and 0.8 μm. If the surface roughness is further reduced by super calendaring to values below 0.4 μm the thickness and stiffness values will generally become below an acceptable level. The ink receiving multilayer of the present invention can be directly applied to the pigment coated base paper. In another embodiment, the pigment coated base paper having a pigmented top side and a back-side is provided on both sides with a polymer resin through high temperature co-extrusion giving a laminated pigment coated base paper. Typically temperatures in this (co-)extrusion are above 280 °C but below 350 °C. The preferred polymers used are poly olefins, particularly polyethylene. In a preferred embodiment the polymer resin of the top side comprises compounds such as an opacifying white pigment e.g. TiO₂ (anatase or rutile), ZnO or ZnS, dyes, coloured pigments, including blueing agents, like e.g. ultramarine or cobalt blue, adhesion promoters, optical brighteners, antioxidant and the like to improve the whiteness of the laminated pigment coated base paper. By using other than white pigments a variety of colors of the laminated pigment coated base paper can be obtained. The total weight of the laminated pigment coated base paper is preferably between 80 and 350 g/m². The laminated pigment coated base paper shows a very good smoothness, which after applying the ink receiving layer of the present invention results in a recording medium with excellent gloss. Examples of the material of the plastic film are polyolefin's such as polyethylene and polypropylene, vinyl copolymers such as polyvinyl acetate, polyvinyl chloride and polystyrene, polyamide such as 6,6-nylon and 6-nylon, polyesters such as polyethylene terephthalate, polyethylene-2 and 6- naphthalate and polycarbonate, and cellulose acetates such as cellulose triacetate and cellulose diacetate. The support may be subjected to a corona treatment in order to improve the adhesion between the support and the ink receiving layer. Also other techniques, like plasma treatment can be used to improve the adhesion. The swellable ink-receiving layer has a dry thickness from 1 to 50 micrometers, preferably from 5 to 25 and more preferably between 8 and 20 micrometers. If the thickness of said ink receiving layer is less than 1 micrometer, adequate absorption of the solvent will not be obtained. If, on the other hand, the thickness of said ink receiving layer exceeds 50 micrometers, no further increase in solvent absorptivity will be gained. The pH of the ink receiving layer should preferably be between 4 and 11 in order to obtain the beneficial effects of this invention. The media of the present invention can be used in any printing application where photographic quality is required. Although the invention is described herein with particular reference to inkjet printing, it will be apparent to the skilled person that the high quality recording media of the present invention are not limited to inkjet recording media (υiz. media suitable to be printed on using inkjet printers), but that it is within the scope of the present invention to provide recording media that are suitable for creating high quality images by using other techniques as well, such as Giclee printing, colour copying, screen printing, gravure, dye-sublimation, flexography, and the like. The media of the present invention show excellent behavior with respect to properties as lightfastness, coloration, beading and glossiness, as is illustrated in more detail by the non-limiting examples given below. In particular, the lightfastness of the media according to the present invention, which may be expressed as the remaining color-density percentage after exposing a sample for 144 hrs using a xenon light (85 000 lx) in an Atlas Wether-O-Meter C I 35A (manufactured by Atlas (Illinois, U.S.A.)), may be 80% or more (density measured using a reflection densitometer (X-Rite 310TR)). Furthermore, the media of the present invention may have an excellent coloration behavior, the coloration of the media upon storage at typical storage conditions being minimal. The coloration (υiz. the "yellowing" of the white parts of the media of the present invention upon aging) may be assessed using a protocol in which L, a*, b* values are measured by a spectrophotometer (e.g. a MINOLTA CM-1000R). The media of the present invention may have a ΔE (whiteness difference, expressed as b* values measured on a spectrophotometer, before and after aging) value after two weeks of storage at 50°C and 40% relative humidity of less than 5, preferably 2 or less. The present invention will be illustrated in detail by the following non-limiting examples. Unless stated otherwise, all ratios given are based on weight. Examples A. Preparation of the overlayer solution-A of the ink receiving layer. A solution containing 50 weight parts of Gelita^® Imagel MA

(dodecenyl-succinic modified acid treated gelatin from Stoess GmbH, Germany (modification grade 40%)) having an IEP of 5.4, 1 weight part of Zonyl^® FSN surfactant (a non-ionic fluoro-carbon type of surfactant), and 949 weight parts of water was prepared at 40 °C. The pH of the solution was adjusted to 8.5 by adding NaOH.

B. Preparation of the acid processed gelatin solution B of the ink receiving layer. A solution containing 100 weight parts of acid pigskin gelatin with an IEP of 9 from Stoess GmbH, Germany and 900 weight parts of water was prepared at 40°C. The pH of the solution was adjusted to 8.5 by adding NaOH. C. Preparation of lime processed gelatin solution C of the ink receiving layer. A solution containing 100 weight parts of lime processed gelatin with an IEP of 5.0 was prepared at 40°C. The pH was adjusted to 8.5 by adding NaOH.

D. Preparation of the gelatin and hydrophilic polymer solution-C A 20 wt.% solution of a lime processed gelatin with an IEP of 5 was prepared at pH 9. An aqueous solution of 10 wt % polyethylene oxide (PEO) having molecular weight of approximately 100 000 (from Sigma Aldrich chemicals, the Netherlands), was also prepared at pH 9. A homogeneous mixture, (υiz. no phase separation occurred), of gelatin and PEO having a weight ratio of 6:1 was made by adding 143 weight parts of said PEO solution and 429 weight parts of water into 428 weight parts of said gelatin solution at a temperature of 40 °C. This mixture was agitated gently for about 30 minutes.

E. Preparation of the gelatin and hydrophilic polymer solution-D Polymer solution-D was prepared in the same way as polymer solution-C. A mixture of gelatin and polyvinyl pyrollidone (PVP) was prepared in the weight ratio of 6 tol wherein PVP having molecular weight of about 30 000 Daltons (ICN Biochemicals).

F. Coating the ink receiving layers Samples were coated according to the formulations shown in Table 1. The layers shown in Table 1 were fed into a slide coating machine, commonly known in the photographic industry, and coated on a photographic grade paper having polyethylene laminated at both sides. The flows of the under-, over- and intermediate layers were adjusted such that, after drying, a total solid content of the intermediate and underlayer(s) (= gelatin + other water soluble polymer) between 8 to 25 g/m² was obtained and a total solid content of the overlayer between 0.5 and 5 g/m². After coating, the coated material was chilled at a temperature of ca. 12 °C to set the gelatin and then dried with dry air at a maximum temperature of 40 °C. G. Schematic drawing and definition of the layer structure: The ink receiving layer consists of at least one underlayer, one intermediate layer and one overlayer as shown in the scheme below.

Table 1: Examples

H. Evaluation of the printed image on the media.

The ink jet media prepared by the above mentioned formulation and said coating process, were printed with a standard image comprising black, cyan, magenta and yellow bars. The image contained also two pictures; including a portrait picture and a composition picture. The image was printed at a room conditions (23°C and 48% Relative Humidity (RH)) and the printed materials were kept at this condition for at least 1 hour to dry. A HP Deskjet ^® 995c was used to print the images by using the following settings: • Print quality : best • Selected Paper type: HP premium plus photo paper, glossy - • Other parameters were according to the factory setting. The quality of the printed images were further analysed visually by analysing the beading behaviour, the glossiness of especially the black area, the dryness of especially the black area, and the bleeding behaviour after some period of time.

1. Definitions of the image evaluation 1. Light fastness Lightfastness is a measure for the dye stability during the display or storage at (ambient) light conditions. In order to evaluate this behaviour a sample was exposed for 144 hrs using a xenon light (85 000 lx) in an Atlas Wether- O -Meter C I 35A, (manufactured by Atlas (Illinois, U.S.A.)). The image __ density of the color on the printed area is measured before and after the xenon exposure and was measured by a reflection densitometer (X-Rite 310TR) and evaluated as the dye residual percentage. The following classification has been defined: O: 80% or more residual percentage Δ: 80-60% residual density X: less than 60% of residual density

2. Beading behaviour As set out hereinabove, beading is defined as the phenomenon that large ink dots that become visible on the printed image. The following classification has been defined: O: no beading is observed Δ: some small spots which is not very visible and/or beading that can be solved by selecting another printer settings. X: Clearly visible 3. Glossiness after printing. The glossiness of the image directly after printing and after two days were analysed by observing the reflection of light on the high density area of the print (e.g. black colour). The more reflection was observed, the glossier the printed image. The following classification was defined for judging the Glossiness: O: Still glossy after 2 days without any defects Δ: Gloss after printing, but after 2 days some "matte" spots was observed. X: Matte appearance after printing, or a lot of "matte" spots after 2 days.

Evaluation result

Changing the water soluble polymer in the underlayer has no effect on the tested properties evaluated above. On the other hand the absence of acid processed gelatin in the intermediate layer clearly has a negative impact on the light fastness and the glossiness.

Claims

1. , Recording medium comprising a support and an ink-receiving layer adhered to said support, wherein the ink receiving layer is a multilayer comprising at least three layers: at least one overlayer comprising at least one type of modified gelatin, at least one underlayer and an intermediate layer comprising an acid processed (modified) gelatin having an iso electric point (IEP) of 6 to 11 in between said at least one overlayer and said at least one underlayer.

2. Medium according to claim 1, wherein the pH of the ink receiving layer is from 4 to 11.

3. Medium according to any of the previous claims, wherein said modified gelatin is selected from the group consisting of acetylated gelatin, phthalated gelatin, alkyl quaternary ammonium modified gelatin, succinated gelatin, alkylsuccinated gelatin, gelatin chemically modified with N- hydroxysuccinimide ester of fatty acid, and combinations thereof.

4. Medium according to any of the previous claims wherein said modified gelatin comprises a C5-C25 alkyl group, a C5-C25 fatty acid group, or both; more preferably a C7-C18 alkyl group, a C7-C18 fatty acid group, or both.

5. Medium according to any of the previous claims, wherein the modified gelatin is used in an amount of 0.1 to 10.0 g/m², more preferably from 0.2 to

5.0 g/m².

6. Medium according to claim 1 in which at least one of the overlayers comprises further at least one fluoro-surfactant, preferably a fluoro-surfactant selected from the group of Li, K and Na- N-perfluoro C4-C13 alkane sulfonyl — N- alkyl glycine, 1,4-bis (fluoroalkyl)-2-[2-N,N,N-trialkylammonium) alkyl amino] butanedioate, and fluorosurfactants having the chemical structure of RfCH2CH2SCH2CH₂CO₂Li or R_fCH2CH2θ(CH₂CH2θ)χH wherein R =

7. Medium according to claimβ, wherein the amount of fluoro-surfactant is from 2.5 to 250 mg/m².

8. , Medium according to any of the previous claims wherein the underlayer and/or the intermediate layer comprises a water soluble polymer selected from the group consisting of polyvinyl alcohol (PVA) based polymers, cellulose derivatives, polyethylene oxide, polyacrylamide, polyvinylpyrollidone or mixtures thereof.

9. Medium according to claim 8, wherein said PVA-based polymer is selected from the group consisting of fully hydrolysed or partially hydrolysed polyvinyl alcohol, carboxylated PVA, acetoacetylated PVA, quaternary ammonium modified PVA, copolymers and terpolymers of PVA with other polymers such as a PVA-NVF polymer according to formula I:

(I) wherein n is between 0 and about 20 mole percent; m is between about 50 and about 97 mole percent; x is between 0 and about 20 mole percent; y is between 0 and about 20 mole percent; z is between 0 and about 2 mole percent and x+y is between about 3 and about 20 mole percent; Ri, and 3 are independently H, 3-propionic acid or Ci-Ce alkyl ester thereof, or is 2-methyl- 3-propionic acid or CI-CG alkyl ester thereof; and R2 and R₄ are independently H or Ci-Ce alkyl.

10. Medium according to any of the previous claims wherein the total amount of gelatin is from 1 to 30 g/m ², preferably from 2 to 20 g/m² and the amount of said water soluble polymer is from 0.1 to 30 g/m², preferably from 0.2 to 20 g/m².

11. _x Medium according to any one of the previous claims, wherein the support is selected from a paper, a base paper, a pigment coated base paper, a laminated pigment coated base paper, a laminated paper, a synthetic paper or a film support.

12. Medium according to any one of the previous claims, wherein the support has a surface roughness Ra smaller than 1.0 μm, preferably smaller than 0.8 μm.

13. Process for preparing a recording medium, comprising the steps of providing at least a first, a second and a third solution, the first solution comprising the modified gelatin for the overlayer of said medium; the second solution comprising the (modified) acid processed gelatin for the intermediate layer; and the third solution for the underlayer, followed by a step wherein said solutions are applied consecutively or simultaneously to a substrate to provide a medium having at least: one overlayer comprising the gelatin from the first solution, at least one underlayer comprising the third solution and one intermediate layer located in between said overlayer and said underlayer comprising the second solution; followed by drying the coated support.

14. A method of forming a permanent, precise ink-jet image comprising the steps of: providing a medium as defined in any of the claims 1- 12; and bringing ink -jet ink into contact with the medium in the pattern of a desired image.