JP2007111883A - Ink jet recording sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jet recording sheet, by which bright white ground having no yellowish tint can be obtained, the yellowing of the white ground part with time is improved and the color reproducibility of a recorded image is excellent. <P>SOLUTION: In the ink jet recording sheet, in which at least one ink accepting layer formed by coating a coating liquid containing fine inorganic particles and a binder on the polyolefin resin coating layer side of a resin-coated paper having a polyolefin resin coating layer on at least one side of a base paper, the polyolefin resin coating layer includes a white pigment and a fluorescent brightener and, at the same time, the ink accepting layer is set to include the fluorescent brightener. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inkjet recording sheet.

  Ink jet recording sheets for photographic image quality are preferably used as a support, so-called resin-coated paper in which at least one of the base papers is coated with polyolefin for the purpose of imparting a high-quality image and water resistance.

In the inkjet recording sheet, in order to obtain a preferable white background without yellowing, a blue pigment is added to the support (for example, see Patent Document 1), and a fluorescent whitening agent is added to the support (for example, Patent Document 1). 2), a blue pigment is added to the ink receiving layer (for example, see Patent Document 3), and a fluorescent whitening agent is added to the ink receiving layer (for example, see Patent Document 4). It can be carried out. However, the method of adding a blue pigment can cancel the yellowing of the white background, but the brightness is lowered and a preferable whiteness cannot be obtained. Further, in the method of adding a fluorescent brightening agent to the ink receiving layer, the fluorescent brightening agent is added to an environment that is easily exposed to air. There is a problem that yellowing increases. On the other hand, in the method of adding a blue pigment to the support, a fluorescent brightening agent can be added to the polyolefin or the undercoat layer of the support. In any case, a high concentration fluorescent brightening agent is added to the thin film. In other words, so-called concentration quenching occurs, and this method alone cannot provide the desired white background, and eventually a combination with a blue pigment must be taken, resulting in a loss of brightness.
JP 2003-3000377 A (Claim 1) JP 2001-310547 A (Claim 1) JP 11-348408 A (Claim 4) JP 2005-126992 A (Claims, Examples)

  The present invention has been made in view of the above problems, and an object thereof is to obtain a bright white background without yellowing, to improve yellowing of the white background portion over time, and to achieve excellent color reproducibility of recorded images. It is to provide a sheet for use.

  The above object of the present invention can be achieved by the following configuration.

  1. For ink jet recording, wherein at least one ink receiving layer is formed by coating a coating liquid containing inorganic fine particles and a binder on the polyolefin resin coating layer side of a resin coated paper having a polyolefin resin coating layer on at least one of the base papers. A sheet for inkjet recording, wherein the polyolefin resin coating layer contains a white pigment and a fluorescent brightening agent, and the ink receiving layer contains a fluorescent brightening agent.

2. 2. The inkjet recording sheet according to 1 above, wherein the hue of an unprinted portion is in the following range with respect to L ^* , a ^* , and b ^* defined by CIE1976.

96 ≦ L ^* ≦ 98
+ 1.5 ≦ a ^* ≦ + 4.0
−12.0 ≦ b ^* ≦ −8.5
3. 3. The ink jet recording sheet as described in 1 or 2 above, which does not contain a blue pigment.

  According to the present invention, a bright white background without yellowing can be obtained, yellowing of the white background portion with time can be improved, and an ink jet recording sheet excellent in color reproducibility of a recorded image can be provided.

  The present invention will be described in more detail. As in the present invention, a fluorescent whitening agent described later is added to the support and a fluorescent whitening agent is also added to the ink receiving layer, so that not only a preferable white background is obtained, but also the white background over time. It has been found that the variation of the color and the color gamut of the resulting image are also enlarged.

  Examples of the fluorescent brightener added to the ink receiving layer include a coumarin derivative, a stilbene derivative, a pyrene derivative, an oxazole derivative, a thiazole derivative, an imidazole derivative, an imidazolone derivative, and a pyrazoline derivative. These fluorescent whitening agents are, for example, Uvitex series and Tinopal series from Ciba Specialty Chemicals, Kayoll series from Nippon Soda Co., Ltd., Whitetex series from Sumitomo Chemical Co., Ltd., Kayaphor series from Nippon Kayaku Co., Ltd., Blankophor series from Bayer Commercially available products can be used. In the case of water-soluble dyes, these optical brighteners may be anionic or cationic depending on the type of water-soluble substituents, and any of them may be used, and oil-soluble dyes should be dispersed and used. You can also.

The fluorescent whitening agent added to the support or the ink receiving layer increases the fluorescence effect as the amount added increases, but as the amount added to the single phase increases, the effect gradually becomes saturated. End up. This is considered to be a decrease in concentration quenching due to an increase in the chance of collision between the fluorescent brightener molecules due to an increase in the concentration of the added fluorescent brightener. In the present invention, the amount of the optical brightener added to the polyolefin resin of the support is preferably 0.01 g / m ² or more and 1.0 g / m ² or less, more preferably 0.02 g / m ² or more and 0.5 g. / m ² or less, the amount is preferably from 0.01 g / m ² or more 1.0 g / m ² or less of the fluorescent brightening agent added to the ink-receiving layer, 0.05 g / m ² or more 0.5 g / m ² The following is more preferable.

  For the purpose of correcting yellowing of the support and obtaining visual whiteness, it has been possible to add blue pigments such as ultramarine to pulp fibers and ink-receiving layers as a bluish color. There was a problem that the white background darkened greatly. For this reason, a smaller amount of blue pigment used for such purposes is more suitable for obtaining a bright white background, and it is preferable not to use it.

A visually preferred white background is affected by both the hue and brightness of the white background. For example, even if a preferable hue is obtained, if the lightness is not sufficiently high, a visually dark white background is obtained, and even if the lightness is sufficiently high, if the hue is shifted, the whiteness is not visually felt. Such visual whiteness can be expressed by L ^* , a ^* , and b ^* defined by CIE1976. In the present invention, 96 ≦ L ^* ≦ 98 is preferable.
+ 1.5 ≦ a ^* ≦ + 4.0
−12.0 ≦ b ^* ≦ −8.5
Range.

(Inorganic fine particles)
The ink receiving layer of the ink jet recording sheet of the present invention is mainly formed from inorganic fine particles and a hydrophilic binder. Examples of the inorganic fine particles forming the ink receiving layer include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, zinc sulfide, Zinc carbonate, hydrotalcite, aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, lithopone, zeolite, magnesium hydroxide, etc. Mention may be made of inorganic pigments. The inorganic fine particles can be used as primary particles or in a state in which secondary agglomerated particles are formed.

  In the present invention, from the viewpoint of obtaining a high-quality print with an ink jet recording sheet, silica or alumina is preferred as the inorganic fine particles, and alumina, pseudoboehmite, colloidal silica, fine particle silica synthesized by a gas phase method, or the like. Particulate silica synthesized by a gas phase method is preferable. Silica synthesized by this vapor phase method may have a surface modified with aluminum, and the aluminum content of the vapor phase silica is 0.05 to 5% by mass with respect to silica. Is preferred.

  The inorganic fine particles may have any particle diameter, but the average particle diameter is preferably 1 μm or less. When it exceeds 1 μm, glossiness or color developability tends to be lowered, and therefore, 200 nm or less is preferable. Further, silica of 100 nm or less is most preferable. The lower limit of the particle size is not particularly limited, but is preferably about 3 nm or more, particularly preferably 5 nm or more from the viewpoint of production of inorganic fine particles.

  The average particle size of the inorganic fine particles is obtained as a simple average value (number average) by observing the cross section and surface of the ink receiving layer with an electron microscope and determining the particle size of 100 arbitrary particles. Here, each particle size is expressed by a diameter assuming a circle equal to the projected area.

  The inorganic fine particles may be present as primary particles or as secondary or higher-order aggregated particles, but the average particle size is independent in the ink receiving layer when observed with an electron microscope. The particle diameter of what forms the particles.

  The average primary particle diameter of the inorganic fine particles needs to be equal to or smaller than the average particle diameter observed in the ink receiving layer, and the primary particle diameter of the inorganic fine particles is preferably 100 nm or less, more preferably 30 nm or less. Most preferred are fine particles of 4 to 20 nm.

The content of the inorganic fine particles in the water-soluble coating solution is 5 to 40% by mass, and particularly preferably 7 to 30% by mass. The inorganic fine particles need to form an ink-receiving layer having sufficient ink-receiving layer properties and less cracking of the film, and the amount of the ink may be 5 to 50 g / m ^{2 in} the ink-receiving layer. preferable. Furthermore, it is particularly preferably 10 to 25 g / m ² .
(Binder)
The hydrophilic binder contained in the ink receiving layer according to the present invention is not particularly limited, and conventionally known hydrophilic binders can be used. Examples thereof include gelatin, polyvinyl pyrrolidone, polyethylene oxide, polyacrylamide, and polyvinyl alcohol. Although it can be used, in the ink jet recording sheet of the present invention, polyvinyl alcohol is particularly preferable as the hydrophilic binder.

  Polyvinyl alcohol interacts with inorganic fine particles, has a particularly high holding power for inorganic fine particles, and is a polymer with relatively low humidity dependency of hygroscopicity, and has a relatively small shrinkage stress during coating and drying. Excellent suitability for cracking during coating and drying. As polyvinyl alcohol preferably used in the present invention, in addition to ordinary polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate, modified polyvinyl alcohol such as polyvinyl alcohol having a cation-modified terminal or anion-modified polyvinyl alcohol having an anionic group. Photocrosslinkable polyvinyl alcohol obtained by crosslinking alcohol, and also polyvinyl alcohol having a crosslinkable group in the side chain under a photoinitiator is also included.

  As the polyvinyl alcohol obtained by hydrolysis of polyvinyl acetate, those having an average degree of polymerization of 300 or more are preferably used, and those having an average degree of polymerization of 1,000 to 5,000 are particularly preferably used. 70 to 100% is preferable, and 80 to 99.8% is particularly preferable.

  Examples of the cation-modified polyvinyl alcohol include polyvinyl having a primary to tertiary amino group or a quaternary amino group in the main chain or side chain of the polyvinyl alcohol as described in JP-A No. 61-10383. These are alcohols, which are obtained by saponifying a copolymer of an ethylenically unsaturated monomer having a cationic group and vinyl acetate.

  Examples of the ethylenically unsaturated monomer having a cationic group include trimethyl- (2-acrylamide-2,2-dimethylethyl) ammonium chloride, trimethyl- (3-acrylamide-3,3-dimethylpropyl) ammonium chloride, Examples thereof include N-vinylimidazole, N-methylvinylimidazole, N- (3-dimethylaminopropyl) methacrylamide, hydroxyethyltrimethylammonium chloride, trimethyl- (3-methacrylamideamidopropyl) ammonium chloride and the like.

  The ratio of the cation-modified group-containing monomer of the cation-modified polyvinyl alcohol is 0.1 to 10 mol%, preferably 0.2 to 5 mol%, relative to vinyl acetate.

  Examples of the anion-modified polyvinyl alcohol include polyvinyl alcohols having an anionic group described in JP-A-1-206088, vinyl alcohols described in JP-A-61-237681 and JP-A-63-307979, and water-soluble. Examples thereof include a copolymer with a vinyl compound having a group, and a modified polyvinyl alcohol having a water-soluble group described in JP-A-7-285265.

  Nonionic modified polyvinyl alcohols include, for example, polyvinyl alcohol derivatives obtained by adding a polyalkylene oxide group described in JP-A-7-9758 to a part of vinyl alcohol, and hydrophobic resins described in JP-A-8-25955. And a block copolymer of a vinyl compound having a functional group and vinyl alcohol.

  Examples of the ultraviolet crosslinking modified polyvinyl alcohol include modified polyvinyl alcohol having a photoreactive side chain as described in JP-A No. 2004-262236.

  Polyvinyl alcohol can be used in combination of two or more, such as the degree of polymerization and the type of modification. In particular, when using polyvinyl alcohol having a degree of polymerization of 2,000 or more, the degree of polymerization is from 0.05 to 10% by weight, preferably 0.1 to 5% by weight, based on the inorganic fine particles. Addition of 2,000 or more polyvinyl alcohol is preferred because there is no significant thickening.

  The ratio of the inorganic fine particles to the hydrophilic binder in the ink receiving layer is preferably 2 to 20 times in terms of mass ratio. If the mass ratio is 2 times or more, an ink-receiving layer having a sufficient porosity can be obtained, and a sufficient void volume can be easily obtained without causing a situation in which voids are blocked by swelling during ink jet recording with a hydrophilic binder that can be maintained. As a result, a high ink absorption speed can be maintained. On the other hand, if this ratio is 20 times or less, cracks are less likely to occur when the ink receiving layer is applied as a thick film. The ratio of the inorganic fine particles to the particularly preferred hydrophilic binder is 2.5 to 12 times, most preferably 3 to 10 times.

(Hardener)
The inkjet recording sheet of the present invention is excellent in glossiness, and it is preferable that polyvinyl alcohol is hardened with a hardener in order to obtain a high porosity without deteriorating the brittleness of the film.

The hardener is generally a compound having a group capable of reacting with polyvinyl alcohol, or a compound that promotes the reaction between different groups of polyvinyl alcohol. For example, an epoxy hardener (diglycidylethyl) is used. Ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-diglycidylcyclohexane, N, N-diglycidyl-4-glycidyloxyaniline, sorbitol polyglycidyl ether, glycerol polyglycidyl ether, etc.) Aldehyde hardeners (formaldehyde, glyoxal, etc.), active halogen hardeners (2,4-dichloro-4-hydroxy-1,3,5-s-triazine, etc.), active vinyl compounds (1,3,3) 5-Trisacryloyl-hexahydro s- triazine, bisvinylsulfonyl methyl ether), boric acid and salts thereof, borax, aluminum alum, and isocyanate compounds.
Of these, boric acid and its salts, epoxy hardeners and isocyanate compounds are preferred.

  As boric acid and salts thereof, oxygen acids having boron atom as a central atom and salts thereof are shown. Specifically, orthoboric acid, diboric acid, metaboric acid, tetraboric acid, pentaboric acid, octaboric acid and salts thereof Is included.

  The amount of the hardener used varies depending on the type of polyvinyl alcohol, the type of hardener, the type of inorganic fine particles, the ratio to polyvinyl alcohol, and the like, but is usually 5 to 500 mg, preferably 10 to 300 mg, per 1 g of polyvinyl alcohol.

  The above hardener may be added to the ink-receiving layer-forming water-soluble coating liquid used in the present invention, or may be added to the ink-receiving layer-forming water-soluble coating liquid (hardener non-hardening agent). The solution can be supplied by overcoating the solution after coating and drying.

(Cationic polymer)
In the ink jet recording sheet of the present invention, a cationic polymer may be used for the ink receiving layer for the purpose of preventing image bleeding due to storage after recording.

Examples of cationic polymers include polyethyleneimine, polyallylamine, polyvinylamine, dicyandiamide polyalkylene polyamine condensate, polyalkylene polyamine dicyandiamide ammonium salt condensate, dicyandiamide formalin condensate, epichlorohydrin-dialkylamine addition polymer, diallyldimethylammonium chloride Polymer, diallyldimethylammonium chloride / SO ₂ copolymer, polyvinyl imidazole, vinyl pyrrolidone / vinyl imidazole copolymer, polyvinyl pyridine, polyamidine, chitosan, cationized starch, vinyl benzyl trimethyl ammonium chloride polymer, (2-methacryloyl) Oxyethyl) trimethylammonium chloride polymer, dimethylaminoethyl methacrylate Over preparative polymer, etc., and cationic polymers are preferred in particular consisting of quaternary amines.

  Examples include the cationic polymers described in Chemical Industry Times, August 15 and 25, 1998, and polymer dye fixing agents described in “Introduction to Polymer Drugs” issued by Sanyo Chemical Industries, Ltd.

The cationic polymer is usually used in the range of 0.1 to 10 g, preferably 0.2 to 5 g, per 1 m ^{2 of the} ink jet recording sheet.

(Polyvalent metal compound)
In the ink jet recording sheet of the present invention, a polyvalent metal compound can be added to the ink receiving layer.

  Examples of the polyvalent metal compound that can be used in the present invention include metal compounds such as aluminum, calcium, magnesium, zinc, iron, strontium, barium, nickel, copper, scandium, gallium, indium, titanium, zirconium, tin, and lead. The polyvalent metal compound may be a polyvalent metal salt. Among them, the compound composed of magnesium, aluminum, zirconium, calcium, and zinc is preferable because it is colorless, the polyvalent metal compound is more preferably a compound containing a zirconium atom, an aluminum atom, or a magnesium atom, and the polyvalent metal compound has a zirconium atom. It is especially preferable that it is a compound containing.

  Further, the compound containing a zirconium atom, an aluminum atom or a magnesium atom that can be used in the present invention may be any of a single salt and a double salt of an inorganic acid or an organic acid, an organic metal compound, a metal complex, etc. The compound itself may be water-soluble or water-insoluble, but those that can be uniformly added to a desired position of the ink receiving layer are preferable.

  The addition layer of the polyvalent metal compound in the present invention is preferably within 60% from the surface of the ink receiving layer thickness, and within this range is at least 80 mol% of the amount of the polyvalent metal compound contained in the entire ink receiving layer. It is particularly preferred.

(Support)
The support used in the present invention is a resin-coated paper (so-called RC paper) having a polyolefin resin coating layer in which a white pigment and a fluorescent brightening agent are added to at least one of the base papers.

  In the present invention, an optical brightener is added to the support. Examples of the method for adding a fluorescent brightener to the support and the fluorescent brightener preferably used include diaminostilbene, imidazole, thiazole, oxazole, triazole, oxadiazole, thiadiazole, and coumarin. , Naphthalimide, pyrazoline, pyrene, imidazolone, benzidine, diaminocarbazole, oxacyanine, methine, pyridine, anthrapyridazine, distyryl, carbostyril, and the like. As a method for addition to the support, since it is formed on the substrate at a high temperature by melt extrusion together with the polyolefin resin, it is preferable that the fluorescent whitening agent can withstand the high temperature at the time of melt extrusion.

  For the purpose of increasing the adhesive strength between the support and the ink receiving layer, the support is preferably subjected to corona discharge treatment, subbing treatment or the like prior to application of the ink receiving layer. Furthermore, the ink jet recording sheet of the present invention is not necessarily colorless, and may be a colored recording sheet.

  In the ink jet recording sheet of the present invention, it is particularly preferable to use a paper support obtained by laminating both sides of a base paper support with polyethylene because the recorded image is close to photographic image quality and a high quality image can be obtained at low cost. Such a paper support laminated with polyethylene will be described below.

  The base paper used for the paper support is made from wood pulp as a main raw material, and if necessary, paper is made using synthetic pulp such as polypropylene or synthetic fiber such as nylon or polyester in addition to wood pulp. As wood pulp, any of LBKP, LBSP, NBKP, NBSP, LDP, NDP, LUKP, and NUKP can be used, but it is preferable to use more LBKP, NBSP, LBSP, NDP, and LDP with a large amount of short fibers. However, the ratio of LBSP and / or LDP is preferably 10% by mass to 70% by mass.

  The pulp is preferably a chemical pulp (sulfate pulp or sulfite pulp) with few impurities, and a pulp having a whiteness improved by bleaching is also useful.

  In the base paper, sizing agents such as higher fatty acids and alkyl ketene dimers, white pigments such as calcium carbonate, talc and titanium oxide, paper strength enhancing agents such as starch, polyacrylamide and polyvinyl alcohol, fluorescent whitening agents, polyethylene glycols A water retaining agent such as a dispersant, a softening agent such as a quaternary ammonium, and the like can be appropriately added.

  The freeness of pulp used in papermaking is preferably 200 to 500 ml as defined by CSF, and the fiber length after beating is 24% by mass as defined in JIS-P-8207, and 42 mesh residue. It is preferable that the sum with the mass% is 30 to 70%. In addition, it is preferable that the mass% of 4 mesh remainder is 20 mass% or less.

  The basis weight of the base paper is preferably 30 to 250 g, particularly preferably 50 to 200 g. The thickness of the base paper is preferably 40 to 250 μm.

The base paper can be given high smoothness by calendering at the paper making stage or after paper making. The density of the base paper is generally 0.7 to 1.2 g / cm ³ (JIS-P-8118). Furthermore, the base paper stiffness is preferably 20 to 200 g under the conditions specified in JIS-P-8143.

  A surface sizing agent may be applied to the surface of the base paper. As the surface sizing agent, a sizing agent similar to the size that can be added to the base paper can be used.

  The pH of the base paper is preferably 5 to 9 when measured by the hot water extraction method defined in JIS-P-8113.

  The polyethylene covering the front and back surfaces of the base paper is mainly low-density polyethylene (LDPE) and / or high-density polyethylene (HDPE), but some other LLDPE, polypropylene, etc. can also be used.

  In particular, the polyethylene layer on the ink receiving layer side preferably has an improved opacity and whiteness by adding rutile or anatase type titanium oxide to the polyethylene, as is widely done in photographic paper. The content of titanium oxide is usually 3% by mass to 20% by mass, preferably 4% by mass to 13% by mass with respect to polyethylene.

  Polyethylene-coated paper can be used as glossy paper. Also, when polyethylene is melt-extruded on the surface of the base paper and coated, a so-called molding process is performed to form a matte or silky surface that can be obtained with ordinary photographic paper. These can also be used in the present invention.

  In the polyethylene-coated paper, the moisture content in the paper is particularly preferably maintained at 3% by mass to 10% by mass.

(Various additives)
In the present invention, various additives other than those described above can be added. For example, aqueous emulsions containing polystyrene, polyacrylic acid esters, polymethacrylic acid esters, urea and similar compounds, and ultraviolet absorbers. , Various known additives such as anti-fading agents, fluorescent whitening agents, light resistance improvers, pH adjusters such as sodium hydroxide and sodium acetate, antifoaming agents, preservatives, thickeners, antistatic agents, matting agents, etc. An agent can also be contained.

(Coating / drying method, etc.)
In the method for producing an ink jet recording sheet, the method for forming the ink receiving layer can be appropriately selected from known coating methods, coated on a support and dried. Examples of the coating method include a roll coating method, a rod bar coating method, an air knife coating method, a spray coating method, a curtain coating method, or US Pat. Nos. 2,761,419 and 2,761,791. A slide bead coating method using an hopper, an extrusion coating method, or the like is preferably used.

  When the slide bead coating method is used, the viscosity of each coating solution when two or more ink receiving layers are simultaneously applied is preferably in the range of 5 to 100 mPa · s, more preferably 10 to 50 mPa · s. It is the range of s. Moreover, when using a curtain application | coating system, the range of 5-1200 mPa * s is preferable, More preferably, it is the range of 25-500 mPa * s.

  Further, the viscosity at 15 ° C. of the coating solution is preferably 100 mPa · s or more, more preferably 100 to 30,000 mPa · s, still more preferably 3,000 to 30,000 mPa · s, and most preferably 10 , 30,000 to 30,000 mPa · s.

  As a coating and drying method, the coating liquid is heated to 30 ° C. or higher, and after simultaneous multilayer coating is performed, the temperature of the formed coating film is once cooled to 1 to 15 ° C. and dried at 10 ° C. or higher. Is preferred. It is preferable to prepare, apply, and dry the coating liquid at a temperature equal to or lower than the Tg of the thermoplastic resin so that the thermoplastic resin contained in the surface layer does not form a film during preparation of the coating liquid, during coating, and during drying. More preferably, the drying conditions are a wet bulb temperature of 5 to 50 ° C. and a film surface temperature of 10 to 50 ° C. Moreover, as a cooling method immediately after application | coating, it is preferable to carry out by a horizontal set system from a viewpoint of the formed coating-film uniformity.

  Moreover, when using photocrosslinking type polyvinyl alcohol as a binder, it is preferable to dry, after irradiating ionizing radiations, such as an ultraviolet-ray and an electron beam, with respect to the coating film formed after application | coating.

(ink)
The recording sheet of the present invention is suitably used as a recording sheet for water-based pigment ink or water-based dye ink which is a colorant-containing ink.

  The water-based dye ink is an ink using a water-soluble dye as a colorant, and is an ink obtained by mixing water or an organic solvent having high miscibility with water as an ink solvent. Examples of the dye include conventionally known azo dyes, xanthene dyes, phthalocyanine dyes, quinone dyes, anthraquinone dyes, etc., which are improved in water solubility by introducing a sulfo group or a carboxy group. Basic dyes are typically used.

  On the other hand, as the pigment used in the pigment ink, various inorganic or organic pigment inks conventionally known by inkjet can be used. Examples of the inorganic pigment ink include carbon black, titanium oxide, and iron oxide. Examples of organic pigments include various azo pigments, phthalocyanine pigments, anthraquinone pigments, quinacridone pigments, indigo pigments, or lake pigments obtained by reacting water-soluble dyes with polyvalent metal ions. Can do.

  These pigment particles are preferably used together with various dispersants and dispersion stabilizers such as hydrophilic polymers and surfactants. The pigment particles are preferably used in which the average particle size is dispersed to about 70 to 150 μm with these dispersed local dispersion stabilizers.

  The concentration of the colorant dye and pigment in the ink depends on the type of the dye or pigment, the type of ink used (whether or not the dark ink is used), and the type of recording paper. It is 0.2-10 mass%.

  Various solvents are used in the colorant-containing ink. As such an ink solvent, water or an organic solvent highly miscible with water can be used alone or mixed with water. Specifically, alcohol solvents such as ethanol, 2-propanol, ethylene glycol, propylene glycol, glycerin, 1,2-hexanediol, 1,6-hexanediol, diethylene glycol monomethyl ether, tetraethylene glycol monomethyl ether, 2- Amides such as pyrrolidinone, N-methylpyrrolidone, N, N-dimethylacetamide, amines such as triethanolamine, N-ethylmorpholine, triethylenetetramine, sulfolane, dimethyl sulfoxide, urea, acetonitrile, acetone, etc. These solvents may be used alone or in combination.

  In addition, various surfactants for the purpose of enhancing the permeability of the ink solvent and other purposes can be used for the colorant-containing ink. As such a surfactant, an anionic or nonionic surfactant is preferably used. Of these, acetylene glycol surfactants are particularly preferred.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto.

Example 1
<Production of support>
The surface of a photographic paper having a water content of 8% and a basis weight of 170 g was extruded and melt coated with a thickness of 35 μm of polyethylene containing 6% by mass of anatase-type titanium oxide and 0.1% by mass of a fluorescent whitening agent (W-1). Polyethylene having a thickness of 40 μm was extruded and melt coated on the back surface. After the corona discharge on the front surface side, polyvinyl alcohol (Kuraray Co., Ltd .: PVA235) was coated with an undercoat layer so as to be 0.05 g per 1 m ² of the recording medium. A back layer containing about 0.4 g of a styrene / acrylate ester latex binder at about 80 ° C., 0.1 g of an antistatic agent (cationic polymer) and 0.1 g of about 2 μm of silica as a matting agent was applied.

<< Preparation of silica dispersion >>
(Preparation of silica dispersion D-1)
4000ml water
17g boric acid
20g borax
600 ml of 25% aqueous solution of cationic polymer (P-1)
Fluorescent whitening agent (Uvitex NFW liq.) 9.09 g
As inorganic fine particles, 1 kg of gas phase method silica (average primary particle diameter of about 12 nm) is prepared, and after adding the above-mentioned additives, it is dispersed with a high pressure homogenizer manufactured by Sanwa Co., Ltd. and finished to 5500 ml with water. Dispersion D-1 was obtained.

(Preparation of silica dispersion D-2)
A silica dispersion D-2 was prepared in the same manner as in the preparation of the silica dispersion D-1, except that the cationic polymer (P-1) was changed to the cationic polymer (P-2).

(Preparation of silica dispersion D-3)
In the preparation of the silica dispersion D-2, the cationic polymer (P-1) was changed to a basic aluminum chloride aqueous solution (manufactured by Taki Chemical Co., Ltd .: Takibine # 1500, 23.75% as Al ₂ O ₃ ). In the same manner, a silica dispersion D-3 was obtained.

<Preparation of inkjet recording sheet>
[Preparation of Sample 101]
The following first to fourth layer coating solutions are applied to the surface of the above-mentioned support so that the wet film thicknesses are 55, 55, 55, and 15 μm, cooled at 5 ° C. for 10 seconds, and then 40 ° C. The sample 101 was prepared by drying with the wind of The amount of the fluorescent whitening agent contained in the sample 101, the support in 0.035 g / m ^2, was the ink-receiving layer 0.15 g / m ^2.

(First layer (lowermost layer) coating solution)
Silica dispersion D-1 550 g
280 g of 6% polyvinyl alcohol (Kuraray PVA235) aqueous solution
Pure water was added to prepare a coating solution so that the total solution was 1000 ml.

(Second layer coating solution)
Silica dispersion D-1 550 g
280 g of 6% polyvinyl alcohol (Kuraray PVA235) aqueous solution
Pure water was added to prepare a coating solution so that the total solution was 1000 ml.

(3rd layer coating solution)
Silica dispersion D-2 550g
280 g of 6% polyvinyl alcohol (Kuraray PVA235) aqueous solution
Zirconyl acetate aqueous solution with a concentration of 20% (Zircozol ZA; diluted with water from Daiichi Rare Element Chemical Industries, Ltd.) 27 g
Pure water was added to prepare a coating solution so that the total solution was 1000 ml.

(Fourth layer (outermost layer) coating solution)
Silica dispersion D-2 550g
280 g of 6% polyvinyl alcohol (Kuraray PVA235) aqueous solution
4 ml of a 4% cationic surfactant (Kao Cotamin 24P)
Pure water was added to prepare a coating solution so that the total solution was 1000 ml.

[Production of Samples 102 to 108]
In Sample 101, Samples 102 to 108 were produced in the same manner except that the fluorescent whitening agent and blue pigment used in the support and ink-receiving layer were changed as shown in Table 1 below. The blue pigment used was ultramarine blue and was added in a small amount to the coating liquid for the first layer in the base paper of the support.

<Evaluation>
The following evaluation was performed on each inkjet recording sheet produced by the above method.

(White background)
L ^* , a ^* , and b ^* defined by CIE 1976 were measured for the white background portion of the obtained ink jet recording sheet. In addition, visual preference for white background was evaluated in the following four stages. A: Both color and brightness are in a preferable range, and B: either color or brightness is in a preferable range. N: Not sufficient level C: Both color and brightness are unfavorable, and aesthetics are impaired. D: At least one of color and brightness is greatly inferior, and aesthetics are significantly impaired.

(Preservation on white background)
The L ^* , a ^* , and b ^* before and after the forced deterioration test under the following conditions was measured on the obtained ink jet recording sheet, and the change in white ΔE was calculated.

Light preservability 70,000 lux light is irradiated for 7 days continuously with a xenon arc lamp.

(Color reproducibility)
Cyan, magenta, yellow, black, red, green, and blue solid patches are printed on the obtained ink jet recording sheet with PM-G800 (manufactured by Seiko Epson Corporation), and then printed on a Gretag Spectrolino color difference meter (manufactured by Gretag). Then, L ^* , a ^* , and b ^* of a total of 8 colors including the white background and the previous 7 colors were measured. Then, L ^* , a ^* , b ^* space volume (GM: GumatVolum) was computed using the measured value. Note that the larger the GM, the higher the color reproducibility.

  From Table 1, it can be seen that the sample of the present invention has a bright white background with no yellowing, improved yellowing of the white background over time, and excellent color reproducibility of the recorded image.

Claims (3)

For ink jet recording, wherein at least one ink receiving layer is formed by coating a coating liquid containing inorganic fine particles and a binder on the polyolefin resin coating layer side of a resin coated paper having a polyolefin resin coating layer on at least one of the base papers. A sheet for inkjet recording, wherein the polyolefin resin coating layer contains a white pigment and a fluorescent brightening agent, and the ink receiving layer contains a fluorescent brightening agent. 2. The ink jet recording sheet according to claim 1, wherein the hue of the unprinted portion is in the following range with respect to L ^* , a ^* , and b ^* defined by CIE1976.
96 ≦ L ^* ≦ 98
+ 1.5 ≦ a ^* ≦ + 4.0
−12.0 ≦ b ^* ≦ −8.5 3. The ink jet recording sheet according to claim 1, which does not contain a blue pigment.