Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/50—Recording sheets characterised by the coating used to improve ink, dye or pigment receptivity, e.g. for ink-jet or thermal dye transfer recording
  • B41M5/52—Macromolecular coatings
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/50—Recording sheets characterised by the coating used to improve ink, dye or pigment receptivity, e.g. for ink-jet or thermal dye transfer recording
  • B41M5/502—Recording sheets characterised by the coating used to improve ink, dye or pigment receptivity, e.g. for ink-jet or thermal dye transfer recording characterised by structural details, e.g. multilayer materials
  • B41M5/508—Supports
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/50—Recording sheets characterised by the coating used to improve ink, dye or pigment receptivity, e.g. for ink-jet or thermal dye transfer recording
  • B41M5/52—Macromolecular coatings
  • B41M5/5218—Macromolecular coatings characterised by inorganic additives, e.g. pigments, clays
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/50—Recording sheets characterised by the coating used to improve ink, dye or pigment receptivity, e.g. for ink-jet or thermal dye transfer recording
  • B41M5/52—Macromolecular coatings
  • B41M5/5227—Macromolecular coatings characterised by organic non-macromolecular additives, e.g. UV-absorbers, plasticisers, surfactants
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/50—Recording sheets characterised by the coating used to improve ink, dye or pigment receptivity, e.g. for ink-jet or thermal dye transfer recording
  • B41M5/52—Macromolecular coatings
  • B41M5/5236—Macromolecular coatings characterised by the use of natural gums, of proteins, e.g. gelatins, or of macromolecular carbohydrates, e.g. cellulose
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/50—Recording sheets characterised by the coating used to improve ink, dye or pigment receptivity, e.g. for ink-jet or thermal dye transfer recording
  • B41M5/52—Macromolecular coatings
  • B41M5/5245—Macromolecular coatings characterised by the use of polymers containing cationic or anionic groups, e.g. mordants
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B41—PRINTING; LINING MACHINES; TYPEWRITERS; STAMPS
  • B41M—PRINTING, DUPLICATING, MARKING, OR COPYING PROCESSES; COLOUR PRINTING
  • B41M5/00—Duplicating or marking methods; Sheet materials for use therein
  • B41M5/50—Recording sheets characterised by the coating used to improve ink, dye or pigment receptivity, e.g. for ink-jet or thermal dye transfer recording
  • B41M5/52—Macromolecular coatings
  • B41M5/5254—Macromolecular coatings characterised by the use of polymers obtained by reactions only involving carbon-to-carbon unsaturated bonds, e.g. vinyl polymers

Definitions

• This invention relates to ink-jet recording sheets suitable for performing recording with ink, and especially to ink-jet recording sheets permitting printing of excellent characteristics and inhibited in image fading and discoloration by storage over extended time and also in dye migration after printing when applied to printers or plotters making use of ink-jet recording.
• Ink-j et recording is a recording technique that performs recording of an image, characters or the like by causing tiny droplets of ink to fly in accordance with one of various operation principles and then allowing them to deposit on a recording medium such as paper.
• Ink-jet recording features high-speed printing performance, low operating noise, applicability for the recording of a wide variety of characters and patterns, easy multi-color printing, and obviation of development and image fixing.
• an image formed by multi-color ink-jet recording can provide a record which is no way inferior to an image printed by multi-color printing making use of a form-plate-dependent printing technique or by a color photographic technique.
• Ink-jet recording has a still further merit in that, when the number of copies or prints to be made is small, ink-jet recording requires lower printing cost than an ordinary printing technique or photographic technique. Ink-jet recording is, therefore, rapidly finding wide-spread utility as image recorders for various information equipment in recent years. For example, ink-jet recording is finding increasing utility in a wide variety of fields in which recording of full-color images is required, for example, output of image designs in design business, production of color block copies in a printing field where the quality of photographic images is required, and production of billboards and catalogs which are frequently updated.
• characteristics the demands for which have arisen with respect to recording media to obtain record images at high resolution and high quality comparable with those of silver halide pictures include:
• printed dots can have high density and can produce vivid and bright tones, (2) high contrast can be produced,
• ink absorption property is so high that, even when printed dots overlap, ink does not run off or bleed
• dots are smooth along their peripheries and are well defined.
• JP 52-53012 A discloses ink-jet recording paper of the ordinary plain paper type equipped with ink absorption property increased by applying a surface- processing coating formulation as a thin layer to a base paper stock of low sizing.
• JP 55-51583 A, JP 59-230787 A and JP 64-11877 A each discloses an ink-jet recording medium of the coated type obtained by applying a coating formulation, which comprises a silicon-containing pigment such as silica and a water-based binder, to a base material to improve the shape and density of dots or tone reproducibility in which the above-described ink-jet recording paper of the ordinary plain paper type had been considered to be poor.
• JP 60-232990 A discloses recording paper provided with a coating layer which contains porous cationic alumina hydrate.
• JP 2- 276670 A, JP 6-48016 A, JP 6-55829 A, JP 7-76161 A, JP 8- 22608 A, JP 10-44585 A, JP 11-34484 A and JP 2000-239578 A disclose recording sheets containing an alumina hydrate of the pseudo-boehmite structure.
• JP 7-76161 A and JP 2000-239578 A disclose recording sheets, each of which contains an alumina sol of the pseudo-boehmite structure and boric acid or a borate salt.
• recorded images were caused to fade by light, nitrogen oxides, sulfur oxides or ozone in the air, or the like in some instances and under specific conditions, non-printed areas and white backgrounds underwent yellowing.
• JP 57-74192 A, JP 57-87989 A and JP 60-72785 A each discloses ink-jet recording paper which contains a phenolic antioxidant and an ultraviolet absorber of the benzophenone or benzotriazole type.
• JP 61-146591 A proposes an ink-jet recording sheet which contains a hindered amine compound
• JP 61-154989 A proposes an ink-jet recording sheet which contains a hydrazide compound
• JP 1-18684 A proposes an ink-jet recording sheet which contains an undecane compound
• JP 1-115677 A proposes an ink-jet recording sheet which contains a thioether compound
• JP 6-286297 A discloses an ink-jet recording sheet which contains a linear polycarboxylic acid
• JP 6-316145 A proposes an ink-jet recording sheet which contains an organic acid having an aromatic nucleus .
• JP 4-34953 B and JP 7-314883 A each discloses an ink-jet recording sheet containing a thiourea derivative, a thiosemicarbazide derivative, a thiocarbohydrazide derivative or the like.
• JP 8-25796 A discloses an ink-jet recording sheet which contains one of a thiourea derivative, a thiosemicarbazide derivative and a thiocarbohydrazide derivative and one of iodine, an iodine compound, a dithiocarbamic acid, a thiocyanate salt and a thiocyanate ester.
• the present invention has as an object the provision of an ink-jet recording sheet which provides high image density, exhibits good tone and ink absorption property, and is inhibited in image fading and discoloration by storage over extended time and also in migration of a dye-containing ink.
• the present inventors have proceeded with various investigations to obtain an ink-jet recording sheet permitting printing of excellent quality and inhibited in image fading and discoloration by storage over extended time and also in dye migration.
• an ink-jet recording sheet having an ink-receiving layer composed, as principal components, of an inorganic pigment and a water-soluble resin and/or a water-dispersible resin
• incorporation of a compound represented by the below- described formula (1) , an acrylamide-diallylamine hydrochloride copolymer and/or a polyallylamine acetate, and a boron compound in the ink-receiving layer makes it possible to achieve the above-described object, leading to the completion of the present invention.
• the present invention therefore, provides an ink-jet recording sheet composed of a base material and at least one ink-receiving layer arranged on at least one side of said base material, characterized in that the ink-receiving layer comprises : at least one binder resin selected from a water-soluble resin and a water-dispersible resin, an inorganic pigment, a compound represented by the following formula (1) :
• R 1 to R 4 may be the same or different and each independently represents a hydrogen atom, an alkyl group, an aryl group or a group represented by -NR 5 R 6 , R 5 and R s each independently represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, a phenyl group or a group represented by -NR 7 CSNR 8 R 9 , R 7 to R 9 may be the same or different and each independently represents a hydrogen atom, an alkyl group having 1 to 5 carbon atoms or a phenyl group, and one of R 1 and R 2 and one of R 3 and R 4 may be fused together to form a ring, at least one cationic resin selected from an acrylamide-diallylamine hydrochloride copolymer and a polyallylamine acetate, and a boron compound; and the inorganic pigment, the compound, the at least one cationic resin and the boron compound satisfy the following equations (1) and (2):
• the inorganic pigment may preferably be at least one of alumina, an alumina hydrate of the boehmite structure and an alumina hydrate of the pseudo-boehmite structure;
• the boron compound may preferably be a boric acid or a borate salt; and
• the base material may preferably be cast-coated paper, baryta paper, polyolefin-resin-coated paper, or a film.
• the ink-jet recording sheet according to the present invention permits printing of excellent characteristics, that is, formation of images with excellent density and tone while exhibiting superb ink absorption property and is inhibited in image fading and discoloration by storage over extended time and also in dye migration.
• the base material for use in the present invention can include base materials composed of paper or the like, such as cast-coated paper, baryta paper, and resin-coated paper both sides of which are coated with a resin such as a polyolefin (hereinafter referred to as "resin-coated paper"), and films.
• the films can include transparent films of thermoplastic resins such as polyethylene, polypropylene, polyesters, polylactic acid, polystyrene, polyacetates, polyvinyl chloride, cellulose acetate, polyethylene terephthalate, polymethyl methacrylate and polycarbonates.
• the inorganic pigment for use in the present invention may preferably be fine inorganic particles, which have high ink-absorbing ability and excellent color producibility and permit formation of images of high quality.
• Illustrative of such fine inorganic particles are calcium carbonate, magnesium carbonate, kaolin, clay, talc, hydrotalcite, aluminum silicate, calcium silicate, magnesium silicate, diatomaceous earth, alumina, colloidal alumina, aluminum hydroxide, alumina hydrates of the boehmite structure, alumina hydrates of the pseudo-boehmite structure, synthetic amorphous silica, colloidal silica, lithopone, and zeolite. These materials can be used either singly or in combination.
• their average particle size may be preferably in a range of from 150 nm to 250 n , more preferably in a range of from 160 nm to 230 nm for obtaining an ink-receiving layer of high gloss and high transparency.
• Inorganic fine particles the average particle size of which is smaller than 150 n lead to a substantial reduction in ink absorption property so that, when printed by a printer of high jetting rate, ink bleeding and beading may occur.
• An average particle size greater than 250 nm results in an ink-receiving layer lowered in transparency and reduced in print density and gloss .
• each "average particle size” as referred to herein can be measured by the dynamic light scattering method, and can be determined from an analysis making use of the cumlant method described in "Polymer Structures (2), Scattering Experiments and Form Observations, Chapter 1: Light
• the present invention is characterized in that an ink-receiving layer is formed by using the compound represented by the formula (1), the acrylamide-diallylamine hydrochloride copolymer and/or polyallylamine acetate, and the boron compound together with the pigment.
• R 1 to R 9 have the same meanings as defined above.
• R 1 to R 4 are alkyl groups, those having 1 to 10 carbon atoms are preferred.
• R 1 to R 4 are aryl groups, phenyl groups or naphthyl groups are preferred. These alkyl and aryl groups may each be unsubstituted or substituted.
• Specific examples of the compound represented by the formula (1) can include those to be described hereinafter. Firstly, illustrative of the compound represented by the formula (1) in which R 1 to R 4 each represents a hydrogen atom, an alkyl group or an aryl group are:
• the compound represented by the formula (1) may be contained preferably in a proportion of from 0.1 to 20 parts by weight per 100 parts by weight of the inorganic pigment.
• the more preferred range is from 0.5 to 15 parts by weight per 100 parts by weight of the inorganic pigment. In this more preferred range, ink bleeding or beading hardly occur upon printing.
• the boron compound is used along with the compound represented by the formula (1) .
• the boron compound for use in the present invention may preferably be an oxyacid formed around a boron atom as a center or a salt thereof, such as boric acid or a borate salt. Specific examples can include orthophosphoric acid, metaphosphoric acid, hypoboric acid, tetraboric acid and pentaboric acid, and salts thereof.
• Boric acid is commonly used as a hardener for improving the film-forming properties, waterproofness and film strength of films formed of hydrophilic polymers. Depending upon the types of reactive groups contained in polymers to be used, various hardeners are chosen, respectively.
• an epoxy hardener or an inorganic hardener such as boric acid or a water-soluble aluminum salt is used.
• the role of the boron compound in the present invention is to increase the fading preventing effect or the discoloration preventing effect for images when incorporated especially along with the compound represented by the formula (1) in the ink-jet recording sheet, and therefore, is different from that of the same compound in the application where its utility is limited to the effect as a hardener.
• the boron compound may be contained preferably in a proportion of from 0.5 to 5 parts by weight per 100 parts by weight of the inorganic pigment. More preferably, the boron compound may be contained in a proportion of from 1 to 5 parts by weight per 100 parts by weight of the inorganic pigment, and the mixing weight ratio of the boron component to the compound represented by the formula (1) may desirably satisfy the following equation (3) :
• an ink-receiving layer by using a cationic resin in combination with the compound represented by the formula (1) and the boron compound.
• the cationic resin can include polyallylamine, polyaminesulfone, polyvinylamine, polyethylene-imine, polyamide-epichlorohydrin resin, polyvinylpyridinium halides, polydimethyldiallylammonium chloride, cation-modified products of polyacrylamide, copolymer of acrylamide with cationic monomer copolymers, copolymers of vinyloxazolidone monomers with other general monomers, and copolymers of vinylimidazole monomers and other general monomers.
• Preferred can be acrylamide-diallylamine hydrochloride copolymers and polyallylamine acetates, each of which is excellent in providing a coating formulation with stability and effectively preventing dye migration upon formation of an ink-receiving layer in the present invention.
• These preferred cationic resins can be used either singly or in combination, and moreover, they can also be used in combination with plural ones of the above-described other cationic resins.
• An acrylamide-diallylamine hydrochloride copolymer which can be preferably used in the present invention is a copolymer represented by the below-described formula (2) and formed from acrylamide and diallylamine hydrochloride as constituents.
• the molar fraction (n) of diallylamine is generally in a range of from 0.1 to 0.99, preferably in a range of from 0.15 to 0.95
• the molar fraction (m) of acrylamide is generally in a range of from 0.01 to 0.9, preferably in a range of from 0.05 to 0.85.
• a diallylamine molar ratio smaller than 0.1 cannot fully bring about waterproofness and the migration preventing effect after ink-jet recording, so that its use in an extremely small molar fraction is not very practical.
• any structure is usable so that the acrylamide-diallylamine hydrochloride copolymer can be in a random, alternate, block or multi-block copolymerization form.
• a polyallylamine acetate which can be preferably used in the present invention is a polyallylamine derivative formed of structural units represented by the following formula (3) : wherein n stands for a positive number indicating a degree
• the weight average molecular weight of the cationic resin employed in the present invention may range preferably from 1,000 to 200,000, more preferably from 5,000 to 200,000.
• a weight average molecular weight lower than 1,000 leads to recorded images of insufficient waterproofness, whereas a weight average molecular weight higher than 200,000 results in a coating formulation the viscosity of which is too high to permit easy handling.
• a cationic resin of high molecular weight tends to lead to a reduction in the efficiency of bonding with dye molecules due to steric hindrance by its molecular structure so that its waterproofness imparting effect cannot be sufficiently brought about especially when it is added in a small proportion.
• the above-described cationic resins which are suitable for use in the present invention, are generally used as dye fixatives to permit formation of images with improved waterproofness on ink-jet recording sheets.
• These dye fixatives each forms a salt with a dye having one or more anionic groups and makes the dye insoluble in water, so that images can be formed with improved waterproofness.
• the acrylamide-diallylamine hydrochloride copolymer and/or the polyallylamine acetate when used in an ink-receiving layer, in which the compound represented by the formula (1) and the boron compound are both contained, as described above, the acrylamide-diallylamine hydrochloride copolymer and/or the polyallylamine acetate can impart waterproofness and the dye migration preventing effect andmoreover, can further improve the effect for the prevention of fading and discoloration of images.
• the proportion of the acrylamide-diallylamine hydrochloride copolymer and/or the polyallylamine acetate to be used also varies depending on the proportion of the inorganic pigment and the proportion of the water-soluble resin and/or water-dispersible resin to be used as a binder. In general, however, it is preferred to add the acrylamide-diallylamine hydrochloride copolymer and/or the polyallylamine acetate in a proportion of from 0.05 to 5 parts by weight per 100 parts by weight of the inorganic pigment.
• the mixing weight ratio of the compound represented by the formula (1), the acrylamide-diallylamine hydrochloride copolymer and/or the polyallylamine acetate and the boron compound to be used in the present invention may preferably be set within the range defined by the following equation (2) :
• (B + C + D) may fall within a range of from 0.65 to 25 parts by weight per 100 parts by weight of the inorganic pigment. If (B + C + D) exceeds 25 parts by weight, the viscosity of a coating formulation used to form an ink-receiving layer will undergo substantial variations with time, possibly leading to a reduction in the stability of coating work. If (B + C + D) is smaller than 0.65 part by weight, on the other hand, the image fading and discoloration preventing effect and the migration inhibiting effect, both of which are objectives of the present invention, may not be fully brought about in some instances .
• the ink-jet recording sheet according to the present invention can be obtained by preparing a coating formulation of the above-described components and then applying the coating formulation to a surface of a base material to form an ink-receiving layer.
• This ink-receiving layer may preferably include voids, which are formed by the inorganic pigment and a small amount of a water-soluble resin and/or a water-dispersible resin.
• voids which are formed by the inorganic pigment and a small amount of a water-soluble resin and/or a water-dispersible resin.
• voids which are formed by the inorganic pigment and a small amount of a water-soluble resin and/or a water-dispersible resin.
• alumina an alumina hydrate of the boehmite structure or an alumina hydrate of the pseudo-boehmite structure as the inorganic pigment is preferred.
• alumina an alumina hydrate of the boehmite structure or an alumina hydrate of the pseudo- boehmite structure, the BET specific surface area of which is at least 50 m 2 /g.
• An alumina hydrate usable in the present invention can be represented by the following formula (4) :
• n stands for any one of integers 0, 1, 2 and 3
• m stands for a value of from 0 to 10, preferably from 0 to 5.
• m can stands for a value which is not an integer. It is to be noted that mmay reach the value of 0 when an alumina hydrate of this sort is subjected to calcination.
• an alumina hydrate showing the boehmite structure is a layer compound the (020) crystal plane of which forms a huge plane, and shows a particular diffraction peak in its X-ray diffraction pattern.
• the boehmite structure it is possible to take, in addition to complete boehmite structure, a structure containing excess water between layers of (020) planes and called "pseudo-boehmite".
• An X-ray diffraction pattern of this pseudo-boehmite shows a broader diffraction peak than complete boehmite.
• complete boehmite and pseudo-boehmite are not clearly distinguishable from each other, they will hereinafter be collectively called an alumina hydrate showing the boehmite structure unless otherwise specifically indicated.
• an aluminum hydrate which is amorphous as determined by its X-ray diffraction can also be used by subjecting it to heat treatment at 50°C or higher in the presence of water and converting its structure into the boehmite structure.
• an alumina compound can be obtained by adding an acid to a long-chain aluminum alkoxide and conducting its hydrolysis and deflocculation.
• long-chain aluminum alkoxide as used herein means an alkoxide having 5 or more carbon atoms. Use of an aluminum alkoxide having 12 to 22 carbon atoms is preferred because such a long-chain aluminum alkoxide facilitates elimination of the alcoholic moiety and shape control of the resulting aluminum hydrate as will be described subsequently herein.
• one or more acids can be chosen at will from organic acids and inorganic acids, and can be used. Nitric acid is most preferred from the standpoint of the efficiency of the hydrolytic reaction and the shape control and dispersibility of the resulting aluminum hydrate.
• a hydrothermal synthesis can be conducted to control the particle size .
• the hydrothermal synthesis is conducted by using an alumina hydrate dispersion which contains nitric acid, the nitric acid in the dispersion is attracted as nitrate groups on surfaces of the alumina hydrate so that the alumina hydrate is improved in water dispersibility.
• the above-described process has a merit in that, compared with production processes of alumina hydrogel or cationic alumina, impurities such as various types of ions can be hardly mixed in. Further, a long-chain aluminum alkoxide has another merit in that, because an alcohol can be readily eliminated subsequent to hydrolysis, the dealcoholation of the alumina hydrate can be effected completely compared with use of a short-chain alkoxide such as aluminum isopropoxide.
• the ink-jet recording sheet according to the present invention can be obtained by mixing a composition, which comprises the inorganic pigment, the compound represented by the formula (1) , the acrylamide-diallylamine hydrochloride copolymer and/or the polyallylamine acetate, and the boron compound, with a water-soluble resin and/or a water- dispersible resin and an aqueous medium in amounts as much as needed into a coating formulation, applying the coating formulation to a surface of a base material and then drying the thus-applied coating formulation into an ink-receiving layer.
• the construction of the ink-jet recording sheet it is possible to choose a construction with an ink-receiving layer arranged on a base material like coated paper or coated film; a construction with an ink-receiving layer formed by impregnating a base material with a portion or a major portion of a coating formulation in the vicinity of a surface of the base material; or a construction with an ink-receiving layer formed by applying a small amount of a coating formulation to a surface of a base material.
• these constructions shall all be embraced by the expression that "an ink-receiving layer is formed on a surface of a base material".
• water-soluble resin and/or water-dispersible resin which is included in the coating formulation are starch, gelatin and casein, and modified products thereof; cellulose derivatives such as methylcellulose, carboxymethylcellulose and hydroxyethylcellulose; completely or partially saponified polyvinyl alcohols and modified products thereof (including those modified with cations, anions, silanols or the like) ; urea resins; melamine resins; epoxy resins; epichlorohydrin resins; polyurethane resins; polyethylene-imine resins; polyamide resins; polyvinyl pyrrolidone resins; polyvinyl butyral resins; pol ( eth) acrylic acid and copolymers thereof; acrylamide resins; maleic anhydride copolymers; polyester resins; SBR latex; NBR latex; methyl methacrylate-butadiene copolymer latex; acrylic polymer latexes such as acrylate ester copolymers; vinyl
• polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate and having an average polymerization degree of from 300 to 5,000. Its saponification degree may preferably be from 70 to lower than 100%, with 80 to 99.5% being particularly preferred.
• These water-soluble or water-dispersible resins can be used either singly or in combination.
• the mixing weight ratio of the inorganic pigment to the water-soluble resin and/or water-dispersible resin in the coating formulation may preferably be in a range of from 1:1 to 30:1, with a range of from 3:1 to 20:1 being more preferred. Setting of the proportion of the water-soluble resin and/or water-dispersible resin within this range makes it possible to provide the resulting ink-receiving layer with resistance to crazing or separation as dust and also with good ink absorption property.
• the aqueous medium in the coating formulation is water or a mixture of water and a water-miscible organic solvent.
• the water-miscible organic solvent can include alcohols such as methanol, ethanol and propanol; lower alkyl ethers of polyhydric alcohols, such as ethylene glycol mono ethyl ether and ethylene glycol dimethyl ether; ketones such as acetone and methyl ethyl ketone; and ethers such as tetrahydrofuran.
• concentration of solids in the coating formulation adapted to form an ink-receiving layer insofar as the coating formulation has a viscosity sufficient to form the ink-receiving layer on the base material.
• the preferred solid concentration may, however, range from 5 to 50% by weight based on the whole weight of the coating formulation.
• a solid concentration lower than 5 wt.% leads to a need for increasing the coat weight to form an ink-receiving layer of sufficient thickness. As longer time and greater energy are required for drying, such a low solid concentration may not be economical in some instances.
• a solid concentration higher than 50 wt.% results in a coating formulation of high viscosity, and the coatability may be reduced in some instances.
• a conventionally-known coating method can be used, such as spin coating, roll coating, blade coating, air knife coating, gate roll coating, bar coating, size pressing, spray coating, gravure coating, curtain coating, rod blade coating, lip coating, or slit die coating. Subsequent to the coating, the surface smoothness of the ink-receiving layer can be improved by using a calender roll or the like as needed.
• the resulting ink-jet recording sheet according to the present invention is provided with an ink-receiving layer the smoothness of which is high without needing any treatment or processing after application of a coating formulation.
• the arithmetic mean roughness (Ra) of the surface of the ink-receiving layer may preferably be 0.1 ⁇ m or lower when measured by setting the cut-off value and measurement length at 0.25 mm and 1.25 mm as specified in JIS-B-0601.
• the preferred range is from 0.5 to 60 g/m 2 , and the more preferred range is from 5 to 55 g/m 2 .
• a coat weight smaller than 0.5 g/m 2 may result in formation of an ink-receiving layer incapable of absorbing water sufficiently from ink so that the ink may run off or an image may bleed.
• a coat weight greater than 60 g/m 2 leads to occurrence of curling on an ink-jet recording sheet upon drying so that concerning printing performance, advantageous e fects may not be brought about to such marked extent as expected.
• the compound represented by the formula (1) and the acrylamide-diallylamine hydrochloride copolymer and/or polyallylamine acetate can be used by adding them directly to a coating formulation as described above or by adding them to an ink-jet recording sheet on which an ink-receiving layer has been formed with the inorganic pigment and other component (s) .
• the compound represented by the formula (1) and the cationic resin (s) can be added to the ink-receiving layer by dissolving or dispersing them in a solvent beforehand and immersing the ink-jet recording sheet in the solution or overcoating the solution to the ink-jet recording sheet.
• the ink-jet recording sheet according to the present invention can be obtained by applying the coating formulation to the base material by one of these coating methods and drying the thus-applied coating formulation in a drier such as a hot air drier, hot drum or far-infrared drier.
• the base material can be provided on one side thereof with an ink-receiving layer or on both sides thereof with ink-receiving layers, respectively. When ink-receiving layers are applied to both sides, respectively, these ink-receiving layers may have the same composition or different compositions.
• other materials can be added to extents not impairing its performance as an ink-jet recording sheet .
• examples of such other materials can include mordant dyes, mordant pigments, dispersants, thickeners, pH adjusters, lubricants, flow modifiers, surfactants, antistatic agents, defoamers, foam inhibitors, penetrants, fluorescent whitening agents, ultraviolet absorbers, and antioxidants .
• the ink-jet recording sheet of the present invention permits printing of excellent quality and especially exhibits superb effects for the inhibition of fading and discoloration of images by storage over extended time, certain interactions appear to take place among the compound represented by the formula (1) , the boron compound and the acrylamide-diallylamine hydrochloride copolymer and/or polyallylamine acetate to develop such effects .
• ink to be used upon making a record on the ink-jet recording sheet according to the present invention. It is, however, preferred to use general water-base ink for ink-jet recording, in which a dye or pigment is used as a colorant, a mixture of water and a water-miscible organic solvent is used as a medium, and the dye or pigment is dissolved or dispersed in the medium.
• ink-jet recording is particularly suited. Any ink-jet recording process can be used insofar as it can apply an ink to an ink-jet recording sheet by effectively causing the ink to fly off from a nozzle.
• a particularly useful process is an ink-jet recording process such as that disclosed in JP 54-59936 A or the like, in which as a result of exposure to action of thermal energy, an ink undergoes a rapid change in volume and the resulting force forces the ink to jet out.
• Ink-jet recording sheets were ranked "A” where no difference in color perception was observed with respect to any of the colors, ink-jet recording sheets were ranked “B” where a slight difference in color perception was observed with respect to at least one of the colors, and ink-jet recording sheets were ranked “C” where a significant difference in color perception was observed with respect to at least one of the colors.
• ⁇ Ranking 2 Migration preventing effect>
• solid printing (ink dot area: 100%) was performed with the single-color inks of yellow (Y) , magenta (M) , cyan (C) and black (Bk) on each ink-jet recording sheet.
• the recorded sheet was exposed for 1 week to an environment of 30°C and 80%RH. Degrees of migration of the individual dyes were visually ranked.
• Ink-jet recording sheets were ranked "A” where no migration took place with respect to any of the colors, ink-jet recording sheets were ranked “B” where slight migration took place with respect to at least one of the colors, and ink-jet recording sheets were ranked "C” where significant migration took place with respect to at least one of the colors.
• aluminum dodexide was prepared. Following the process disclosed in U.S. Patent No. 4,242,271, aluminum dodexide was prepared. Following the process disclosed in U.S. Patent No. 4,202,870, the aluminum dodexide was then hydrolyzed to prepare an alumina slurry. Water was added to the alumina slurry until the content of an alumina hydrate having the boehmite structure reached 7.7%. At that time, the pH of the alumina slurry was 9.4. A 3.9% nitric acid solution was added to the slurry to adjust its pH.
• the slurry pre-aging pH: 6.0
• aging temperature: 150°C, aging time: 6 hours aging temperature: 150°C
• aging time: 6 hours aging temperature: 150°C
• the powder so obtained was an alumina hydrate, the particle shape and crystal structure of which were plate-like and the boehmite structure, respectively.
• the alumina hydrate powder having the boehmite structure was mixed at a concentration of 17% in deionized water to prepare an alumina hydrate dispersion A.
• the alumina hydrate dispersion A was agitated at 2,000 rpm for 5 minutes in a homomixer (manufactured by Tokushu Kika Kogyo Co., Ltd.) to obtain a dispersion B.
• a dispersion B 100 parts
• N,N' -diethylthiourea (0.340 part, 2% based on the alumina hydrate)
• boric acid 22.67 parts, 4% based on the alumina hydrate
• “SumirezResin 1001" 0.567 part, 1% based on the alumina hydrate: trade name for an acrylamide-diallylamine hydrochloride copolymer, 30% aqueous solution; product of Sumitomo Chemical Co., Ltd.
• An ink-jet recording sheet was prepared in a similar manner as in Example 1 except that the amounts of the 3% aqueous solution of boric acid and "SumirezResin 1001" were changed to 11.33 parts (2% based on the alumina hydrate) and 0.283 part (0.5% based on the alumina hydrate), and ranking and measurement tests were conducted. The results are presented in Table 1.
• Example 3 An ink-jet recording sheet was prepared in a similar manner as in Example 1 except that N,N' -dimethylthiourea (0.170 part, 1% based on the alumina hydrate) was used in place of N,N' -diethylthiourea and the amounts of the 3% aqueous solution of boric acid and "SumirezResin 1001" were changed to 5.67 parts (1% based on the alumina hydrate) and 0.057 part
• Example 4 An ink-jet recording sheet was prepared in a similar manner as in Example 1 except that thiosemicarbazide (2.55 parts, 15% based on the alumina hydrate) was added in place of N,N' -diethylthiourea and the amounts of the 3% aqueous solution of boric acid and "SumirezResin 1001" were changed to 5.67 parts (1% based on the alumina hydrate) and 1.70 parts
• Example 5 An ink-jet recording sheet was prepared in a similar manner as in Example 4 except that the amounts of thiosemicarbazide and "SumirezResin 1001" were changed to
• Example 6 An ink-jet recording sheet was prepared in a similar manner as in Example 4 except that the amount of the 3% aqueous solution of boric acid was changed to 28.33 parts (5% based on the alumina hydrate) , and ranking and measurement tests were conducted. The results are presented in Table 1.
• Example 7 An ink-jet recording sheet was prepared in a similar manner as in Example 4 except that the amount of the 3% aqueous solution of boric acid was changed to 28.33 parts (5% based on the alumina hydrate) , and ranking and measurement tests were conducted. The results are presented in Table 1.
• Example 7 An ink-jet recording sheet was prepared in a similar manner as in Example 4 except that the amount of the 3% aqueous solution of boric acid was changed to 28.33 parts (5% based on the alumina hydrate) , and ranking and measurement tests were conducted. The results are presented in Table 1.
• Example 7 An ink-jet recording sheet was prepared in a similar manner as in Example 4 except that the amount of the 3%
• An ink-jet recording sheet was prepared in a similar manner as in Example 2 except that "PAA-CH 3 C0 2 H-L" (trade name for polyallylamine acetate, 25% aqueous solution; product of Nitto Boseki Co., Ltd.) was added in a proportion of 0.340 part (0.5% based on the alumina hydrate) in place of "SumirezResin 1001", and ranking and measurement tests were conducted. The results are presented in Table 1.
• PAA-CH 3 C0 2 H-L trade name for polyallylamine acetate, 25% aqueous solution; product of Nitto Boseki Co., Ltd.
• Example 8 An ink-jet recording sheet was prepared in a similar manner as in Example 2 except that "PAA-CH 3 C0 2 H-L” was added in a proportion of 0.680 part (1% based on the alumina hydrate) in place of "SumirezResin 1001", and ranking and measurement tests were conducted. The results are presented in Table 1.
• Example 9 An ink-jet recording sheet was prepared in a similar manner as in Example 2 except that "PAA-CH 3 C0 2 H-L" was added in a proportion of 0.680 part (1% based on the alumina hydrate) in place of “SumirezResin 1001", and ranking and measurement tests were conducted. The results are presented in Table 1.
• Example 9 An ink-jet recording sheet was prepared in a similar manner as in Example 2 except that "PAA-CH 3 C0 2 H-L" was added in a proportion of 0.680 part (1% based on the alumina hydrate) in place of "SumirezResin 1001", and ranking and measurement
• Example 10 An ink-jet recording sheet was prepared in a similar manner as in Example 2 except that the amount of the 3% aqueous solution of boric acid was changed to 5.67 parts (1% based on the alumina hydrate) and "PAA-CH 3 C0 2 H-L" was added in a proportion of 3.06 parts (4.5% based on the alumina hydrate) in place of "SumirezResin 1001", and ranking and measurement tests were conducted. The results are presented in Table 1.
• Example 10 An ink-jet recording sheet was prepared in a similar manner as in Example 2 except that the amount of the 3% aqueous solution of boric acid was changed to 5.67 parts (1% based on the alumina hydrate) and "PAA-CH 3 C0 2 H-L" was added in a proportion of 3.06 parts (4.5% based on the alumina hydrate) in place of "SumirezResin 1001", and ranking and measurement tests were conducted. The results are presented in Table 1.
• Example 10 An ink-jet recording
• Example 2 An ink-jet recording sheet was prepared in a similar manner as in Example 2 except that "PAA-CH 3 C0 2 H-L" (0.340 part, 0.5% based on the alumina hydrate) was additionally added, and ranking and measurement tests were conducted. The results are presented in Table 1. Comparative Example 1 An ink-jet recording sheet was prepared in a similar manner as in Example 2 except that "SumirezResin 1001" was not added, and ranking and measurement tests were conducted. The results are presented in Table 1. Comparative Example 2
• Example 2 An ink-jet recording sheet was prepared in a similar manner as in Example 2 except that N,N' -diethylthiourea was not added, and ranking and measurement tests were conducted. The results are presented in Table 1. Comparative Example 3
• An ink-jet recording sheet was prepared in a similar manner as in Example 2 except that "PAA-HC1-3L” (trade name for polyallylamine acetate, 50% aqueous solution; product of Nitto Boseki Co., Ltd.) was added in a proportion of 0.170 part (0.5% based on the alumina hydrate) in place of "SumirezResin 1001", and ranking and measurement tests were conducted.
• PAA-HC1-3L trade name for polyallylamine acetate, 50% aqueous solution; product of Nitto Boseki Co., Ltd.
• An ink-jet recording sheet was prepared in a similar manner as in Example 2 except that "Sunfix 414" (trade name for polyalkylenepolyamine-dicyandiamide polycondensation product, 50% aqueous solution; product of Sanyo Chemical
• An ink-jet recording sheet was prepared in a similar manner as in Example 2 except that "PAS-M-1" (trade name for diallylmethylamine hydrochloride polymer, 60% aqueous solution; product of Ni.tto Boseki Co., Ltd.) was added in a proportion of 0.142 part (0.5% based on the alumina hydrate) in place of "SumirezResin 1001", and ranking and measurement tests were conducted.
• PAS-M-1 trade name for diallylmethylamine hydrochloride polymer, 60% aqueous solution; product of Ni.tto Boseki Co., Ltd.
• An ink-jet recording sheet was prepared in a similar manner as in Example 4 except that the amounts of thiosemicarbazide and the 3% aqueous solution of boric acid were changed to 3.40 parts (20% based on the alumina hydrate) and 17.0 parts (3% based on the alumina hydrate) , respectively, and ranking and measurement tests were conducted. The results are presented in Table 1.
• the ink-jet recording sheets according to the present invention each of which contained the compound represented by the formula (1) , the specific cationic resin and the boron compound in its ink-receiving layer effectively inhibited ozone-related discoloration and fading of images and was excellent in indoor image fastness. At the same time, dye migration under an environment of high temperature and high humidity was also prevented, thereby exhibiting superb storability of images over extended time. Furthermore, the use of the construction of an ink-receiving layer according to the present invention in combination with a base material having high smoothness, such as resin-coated paper or a film, made it possible to obtain a surface of high smoothness without needing any additional treatment or processing after the coating.
• a base material having high smoothness such as resin-coated paper or a film
• Incorporation of a compound represented by the formula (1), an acrylamide-diallylamine hydrochloride copolymer and/or polyallylamine acetate and a boron compound at a specific ratio in an ink-receiving layer can provide an ink-jet recording sheet permitting printing of excellent quality and inhibited in image fading and discoloration by storage over extended time and also in dye migration.

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