JP2005262461A - Inkjet recording medium, and inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording medium in which a difference in gloss between a non-printed section and an image section is reduced when printing is performed with a pigmented ink, and the expansion of a dot diameter, water-resistance, scratch-resistance, and folding-resistance are increased, and to provide an inkjet recording method using the inkjet recording medium. <P>SOLUTION: This inkjet recording medium has a surface layer containing an inorganic particle of which the average index of refraction is 2.1 to 2.9, and a binder on a supporting body. Then, a hydrogen bonding component for surface tension in the surface layer is 25 to 50 mN/m. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a novel ink jet recording medium and an ink jet recording method.

  In recent years, there has been remarkable progress in inkjet recording systems. Inkjet recording is a system in which an ink liquid containing a color material is ejected from a thin nozzle onto an inkjet recording medium to form an image. Therefore, a water-soluble dye that is soluble in water has been used as a color material from the beginning. Ink-jet recording media have also emerged, so-called swollen or void-type recording media that incorporate dyes into ink-jet recording media along with ink liquids to improve image quality. Development has been promoted with the goal of improving image quality such as prevention, image resistance, light resistance, ozone fading, and so on. However, with dyes, since the durability of the dyes themselves is low, it has not been possible to obtain images that require high image storage stability.

  On the other hand, an ink jet recording method using a pigment as a coloring material has been proposed aiming at high image storage stability. This is an ink containing a pigment dispersion in which a pigment is dispersed. Since the pigment itself has high light resistance and ozone fading resistance, the image storability of the formed image is compared with the image using a dye. Then, it can raise remarkably. However, in the ink using the pigment, the pigment does not soak into the ink jet recording medium and exists in the vicinity of the surface. As a result, the gloss of the image portion becomes high, and there is a difference in gloss between the image forming portion and the non-printing portion. In addition, the pigment does not soak into the ink jet recording medium, and therefore, when the surface of the image is rubbed, scratches or the like are likely to occur, and the dot diameter is smaller than that of the dye image. The problem is that the density does not increase, and in addition, when forming images with various inks, if the surface tension of each ink is different, the dot diameter will fluctuate greatly due to the influence of surface surface force. A new problem has emerged that the density of the resulting image will vary greatly.

  In order to solve the above-mentioned problems, generally, an ink jet recording medium having an uneven surface, diffusing reflected light and making the difference in gloss inconspicuous, and reducing the contact area is used for pigment ink. ing. However, as a result of making the surface uneven, there are disadvantages that the overall gloss is reduced and only a rough image can be obtained, and that the dot diameter does not widen and the image density is still reduced. .

  As an attempt to solve the above problems, an ink jet recording medium (for example, see Patent Documents 1 and 2) having a structure in which functions imparted by a pigment fixing layer and a solvent absorbing layer are separated, or a refractive index of 1.65 or more. By using titanium oxide and colloidal silica for the protective layer in an ink jet recording medium (for example, see Patent Document 3) having spherical particles arranged on the surface or a two-layer structure of a protective layer and an ink receiving layer, image color Ink jet recording media (see, for example, Patent Document 4) with improved properties and coating strength have been proposed.

The methods proposed in each of the above-mentioned patent documents can provide a certain level of gloss difference between the non-printed portion (white background) and the image portion, and an improvement in image density, but the degree of improvement is never sufficient. It is difficult to say and the current situation is that further improvements are required.
JP 2000-127613 A Japanese Patent Laid-Open No. 2002-211113 JP 2001-328341 A JP 2001-10212 A

  The present invention has been made in view of the above problems, and its purpose is to reduce the difference in gloss between the non-printing part and the image part when printing with pigment ink, and to increase the dot diameter, water resistance, An ink jet recording medium having improved scratch resistance and bending resistance and an ink jet recording method using the same.

  The above object of the present invention is achieved by the following configurations.

(Claim 1)
It has a surface layer containing inorganic fine particles having an average refractive index of 2.1 to 2.9 and a binder on the support, and the hydrogen bond component of the surface tension in the surface layer is 25 to 50 mN / m. An inkjet recording medium characterized by the above.

(Claim 2)
2. The ink jet recording medium according to claim 1, wherein a product S of a center line surface roughness Ra (μm) of the surface layer and an average refractive index of the inorganic fine particles is 1.7 μm or less.

(Claim 3)
The ink jet recording medium according to claim 1, wherein the surface layer contains a hydrogen bonding cationic substance.

(Claim 4)
The inorganic fine particles contained in the surface layer are at least one selected from titanium oxide, cerium oxide, and zirconium oxide, and silica or alumina. Inkjet recording medium.

(Claim 5)
The inkjet recording medium according to any one of claims 1 to 4, further comprising a solvent absorption layer between the surface layer and the support.

(Claim 6)
6. The solvent absorbing layer is a porous layer containing inorganic fine particles having an average refractive index of 1.3 to 1.7 and an average particle diameter of 1 to 200 nm and a binder. 2. An ink jet recording medium according to 1.

(Claim 7)
The inkjet recording medium according to claim 6, wherein the porous layer is cationic.

(Claim 8)
The inkjet recording medium according to claim 1, wherein the support is resin-coated paper.

(Claim 9)
An ink jet recording method comprising: recording an image by discharging an ink containing at least a water-soluble solvent and a pigment onto the ink jet recording medium according to claim 1.

  According to the present invention, when printing with pigment ink, the gloss difference between the non-printing portion and the image portion is reduced, the dot diameter is expanded, and the water resistance, scratch resistance and bending resistance are improved. A medium and an ink jet recording method using the medium can be provided.

  Hereinafter, the best mode for carrying out the present invention will be described in detail.

  As a result of intensive studies in view of the above problems, the present inventor has a surface layer containing inorganic fine particles having an average refractive index of 2.1 to 2.9 and a binder on the support. An inkjet recording medium (hereinafter, also simply referred to as a recording medium) having a hydrogen bond component of surface tension of 25 to 50 mN / m provides a uniform glossy feeling over the white background and the image area, and changes in the surface tension of the pigment ink. Regardless of this, the present invention has found that an image can be obtained in which the image density in the highlight portion is high and an image having a high gradation can be obtained, and an ink jet recording medium excellent in scratch resistance and bending resistance can be obtained. It depends on you.

  Furthermore, in addition to the above configuration, by making the product of the surface roughness of the surface layer and the average refractive index of the inorganic fine particles of the surface layer 1.7 μm or less, the gloss value is increased, and an image close to a silver salt photograph is also visible. By providing a solvent absorbing layer between the surface layer and the support, it is possible to prevent image quality deterioration due to ink overflow during ink jet recording.

  In general, the dot diameter of ink for ink jet recording (hereinafter also simply referred to as ink) is explained by wettability with a recording medium. The surface energy of a recording medium is larger, and the smaller the surface energy of ink is, the more ink is recorded on the recording medium. It is said that the dot diameter greatly fluctuates due to well-wetting, spreading of the dots, and fluctuations in the surface tension of the ink to be printed. However, as a result of examining the dot diameter of the pigment ink, it was found that this wettability alone cannot explain. The reason for this is that pigment ink, unlike dye ink, has color material in the ink in the state of particles, causing aggregation on the surface of the recording medium. There was a case where it didn't get bigger. Therefore, the characteristics of the recording medium on which dots are stably formed were examined. As a result, it was found that the hydrogen bond component was greatly involved in the dot diameter among the components obtained by decomposing the surface energy into three components. The hydrogen bond component γh of the surface energy of the surface layer referred to in the present invention is one component of the surface tension decomposed into three components of a dispersed component, a polar component, and a hydrogen bond component by the extended Fowkes equation.

  When this hydrogen bonding component is in the range of 25 to 50 mN / m, the dot diameter is sufficiently widened, the density of the highlight portion is increased, and an image rich in gradation is obtained, regardless of the change in the surface tension of the ink. I found that I could always get big dots. Furthermore, it has been found that when the range of the hydrogen bond component is within the range, the image portion is hardly damaged when the image portion is bent. Although this is not imagined, it is considered that the dispersant covering the pigment surface is hydrogen-bonding, and this dispersant is firmly bonded to the recording medium.

  In the present invention, in order to make the hydrogen bonding component of the surface layer in the range of 25 to 50 mN / m defined in the present invention, inorganic fine particles having an average refractive index of 2.1 to 2.9, and the inorganic fine particles and adsorption It is preferable to add a hydrogen-bonding cationic substance that improves the combination of inorganic fine particles, the binder, and the surface hydrogen bonding component. When the hydrogen bond component is less than 25 mN / m, the image density and the bending resistance are insufficient. When the hydrogen bond component exceeds 50 mN / m, a film as a surface layer is not formed, and durability such as scratch resistance deteriorates.

  Furthermore, the solvent absorption layer provided between the surface layer and the support is a porous layer containing inorganic fine particles having an average refractive index of 1.3 to 1.7 and an average particle diameter of 1 to 200 nm and a binder. As a result, the ink absorption capacity is further increased. Therefore, by setting the hydrogen bond component of the surface tension in the surface layer to 25 to 50 mN / m, it is possible to prevent ink overflow, and in addition, silica is added to the surface layer. By containing fine particles, the ink absorption speed can be increased, so that deterioration of image quality due to ink overflow during ink jet recording can be prevented.

  By containing a polymer capable of adjusting the hydrogen bonding component of the surface layer to a range of 25 to 50 mN / m, the fixability of the pigment can be improved, the water resistance and the bleeding resistance can be improved, and the porous layer has a cation. By containing the functional polymer, the dispersibility of the inorganic fine particles contained in the porous layer can be increased, so that the surface roughness can be reduced and the gloss can be increased. Further, the use of resin-coated paper as a support can further increase the water resistance.

  Details of the present invention will be described below.

[Surface layer]
(Inorganic fine particles)
The inorganic fine particles used in the surface layer according to the present invention are inorganic fine particles having an average refractive index of 2.1 to 2.9.

  The average refractive index in the present invention refers to the refractive index when the inorganic fine particles are composed of one kind. Further, when the inorganic fine particles are composed of a plurality of types, the refractive index is averaged by the mass fraction of each inorganic fine particle, and the mass fraction is calculated from the refractive index of each individual inorganic fine particle and the composition ratio of the inorganic fine particles. Can be obtained by calculation. For example, the average refractive index of inorganic fine particles having a composition of titanium oxide (refractive index = 2.76): silica (refractive index = 1.44) = 2: 1 (mass ratio) is (2.76 × 2/3). ) + (1.44 × 1/3) = 2.32. Regarding the refractive index of inorganic fine particles, many measured values are published in publicly known literature.

  Examples of such inorganic fine particles include titanium oxide (rutile type, refractive index = 2.76), titanium oxide (anatase type, 2.52), zirconium oxide (2.40), cerium oxide (2.21), three Examples thereof include ferric oxide (2.9) and antimony oxide (2.19). Among these, one selected from titanium oxide, cerium oxide and zirconium oxide is preferable from the viewpoint of securing a white background on the surface of the recording medium. Further, if the average refractive index is in the range of 2.1 to 2.9, the individual inorganic fine particles include inorganic fine particles having a lower refractive index, such as α-alumina (1.8), γ-alumina. (1.7), alumina (1.56), magnesium hydroxide (1.52), silica (1.44), and tin oxide (2.093) can be used in combination. In particular, titanium oxide is particularly preferable from the viewpoint of cost because it has a high refractive index and brings about a large effect in a small amount.

  In the recording medium of the present invention, the product of the center line surface roughness Ra (μm) of the surface layer and the average refractive index is preferably 1.7 μm or less. Even if the product is larger than 1.7 μm, a uniform gloss can be obtained on a white background and an image, but if it is 1.7 μm or less, the 60 ° gloss value is increased, and a better gloss can be obtained. The centerline surface roughness in the present invention can be measured using, for example, RST / PLUS manufactured by WYKO.

  The surface roughness is preferably as small as possible from the viewpoint of preventing light scattering. Light scattering is affected by the surface roughness and the refractive index of the surface layer, but in the present invention, it is preferable to reduce the surface roughness because the surface layer uses inorganic fine particles having a high refractive index as described above. The product is preferably 1.7 μm or less.

  The average primary particle diameter of the inorganic fine particles having an average refractive index of 2.1 to 2.9 is preferably 1 to 200 nm. If the average primary particle diameter is within this range, there is no particular limitation, but a range of 5 to 80 nm is particularly preferable. By setting the average primary particle diameter to 1 nm or more, the gap through which the surface ink passes becomes large. Further, ink absorption is improved and ink overflow can be further prevented. Moreover, by setting it as 200 nm or less, surface roughness becomes low and gloss can be improved further.

(binder)
As the binder used in the surface layer according to the present invention, a conventionally known hydrophilic resin is used. Examples of known hydrophilic resins include gelatin, polyvinyl pyrrolidone, pullulan, polyvinyl alcohol or derivatives thereof, polyethylene glycol, hydroxyethyl cellulose, dextran, dextrin, water-soluble polyvinyl butyral, and the like.

  The amount of the binder added is not limited as long as it is an amount that does not desorb the inorganic fine particles in the surface layer, but is used in a range of 1 to 200% by mass ratio with respect to the inorganic fine particles. Preferably it is 5 to 50%. When it is larger than 1%, the bonding of the surface layer becomes strong and the scratch resistance is further improved. Moreover, if it is 200% or less, ink absorptivity will increase and ink overflow can be prevented further.

(Hydrogen bonding cationic substance)
In the present invention, it is preferable to add a hydrogen bonding cationic substance to the surface layer for fixing the pigment ink. As the cationic substance, either an inorganic cationic compound or a cationic polymer composed of an organic polymer may be used. However, in order to increase the surface hydrogen bonding component and increase the concentration of the highlight portion, Cationic compounds are preferred. The hydrogen bonding cationic compound means a compound having a large number of hydroxyl groups capable of hydrogen bonding among inorganic cationic compounds and cationic polymers.

  As the inorganic cationic compound, for example, general compounds such as calcium acetate, calcium chloride, calcium formate, calcium sulfate, barium acetate, barium sulfate, barium phosphate and magnesium nitrate can be used.

  Among these, the water-bonding cationic compound is preferably a water-soluble aluminum compound or a water-soluble compound containing a Group 4A element of the periodic table. As the water-soluble aluminum compound, for example, aluminum chloride or a hydrate thereof, aluminum sulfate or a hydrate thereof, ammonium alum or the like is known as an inorganic salt. Furthermore, there is a basic polyaluminum hydroxide compound which is an inorganic aluminum-containing cationic polymer. In particular, a basic polyaluminum hydroxide compound is preferable.

  Examples of the cationic polymer include cationic polymers having a primary to tertiary amino group and a quaternary ammonium base. Among these, as the hydrogen bonding cationic compound, a cationic polymer having a primary to tertiary amino group is preferable.

Examples of the cationic polymer preferably applicable to the present invention include polyethyleneimine, polyallylamine, polyvinylamine, dicyandiamide polyalkylene polyamine condensate, polyalkylene polyamine dicyandiamide ammonium salt condensate, dicyandiamide formalin condensate, epichlorohydrin dialkylamine polycondensation. things, diallyl dimethyl ammonium chloride-SO ₂ copolymer, polyvinyl imidazole, polyvinyl pyrrolidone, vinyl imidazole copolymers, polyvinyl pyridine, polyamidine, chitosan, cationized starch, vinylbenzyltrimethylammonium chloride polymers, (2-methacryloyloxy-oxy ) Trimethylammonium chloride polymer, dimethylaminoethyl methacrylate polymer, etc. However, as a more preferable hydrogen bonding cationic substance, polyethyleneimine, polyallylamine, dicyandiamide polyalkylene polyamine condensate, polyalkylene polyamine dicyandiamide ammonium salt condensate, dimethylaminoethyl methacrylate polymer polyvinylamine, dimethylaminoethyl methacrylate polymer Can be mentioned.

(Additives / Others)
Various additives other than those described above can be added to the surface layer. Such additives include, for example, cross-linking agents, surfactants (cations, nonions, anions, amphoteric), white background tone modifiers, fluorescent whitening agents, antifungal agents, viscosity modifiers, low-boiling organic solvents, high A boiling organic solvent, latex emulsion, anti-fading agent, and ultraviolet absorber may be added.

  The thickness of the surface layer is not particularly limited, but is preferably 0.01 to 100 μm from the viewpoint of coating film formation. In this range, a uniform coating film can be obtained without causing a coating failure or the like. More preferably, it is 0.01-0.3 micrometer or 1.2-100 micrometers from a viewpoint of preventing the interference fringe of light, More preferably, it is 0.02-0.3 micrometer or 1.2-20 micrometers.

(Solvent absorption layer)
In order to increase the ink absorption capacity and obtain a high-density image, it is preferable to provide a solvent absorption layer between the surface layer and the support. The solvent absorption layer is roughly classified into a porous layer and a swelling layer.

(Porous layer)
<Inorganic fine particles>
The porous layer is formed by mixing inorganic fine particles and a water-soluble binder and is characterized by forming voids in the layer. The inorganic fine particles used for the porous layer are inorganic fine particles having an average refractive index of 1.3 to 1.7 and an average particle diameter of 1 to 200 nm.

  The average refractive index of the inorganic fine particles used for the porous layer is synonymous with the average refractive index of the inorganic fine particles used for the surface layer. The average particle diameter is obtained by converting a circle-converted average particle diameter obtained from an average value of projected areas (determined for at least 100) of a transmission electron microscope (TEM) photograph into a spherical shape.

  Examples of such inorganic fine particles include γ-alumina (1.7), alumina (1.56), magnesium hydroxide (1.52), silica (1.44), and the like. Among these, silica fine particles or alumina particles are preferable because the voids can be increased, so that a large amount of solvent can be absorbed. Particularly preferred are silica fine particles. As silica fine particles, silica synthesized by an ordinary wet method, silica synthesized by a vapor phase method, and the like are preferably used, but fine particle silica synthesized by a vapor phase method is particularly preferable because of increasing the number of voids.

  Wet silica is synthesized by precipitation or gel method using sodium silicate or the like as a raw material. The average particle size of wet silica is required to be 1 to 200 nm. If the average particle size is within this range, there is no particular limitation on the lower limit for the primary particle size of each wet silica, but it is 3 nm or more from the viewpoint of the production stability of silica particles, and 200 nm from the viewpoint of the transparency of the film. The following is preferable.

  Vapor phase method silica is synthesized by combustion method using silicon tetrachloride or the like and hydrogen as raw materials.

  As for the particle diameters of wet silica and vapor-phase process silica, the average primary particle diameter is preferably 1 to 200 nm, more preferably 1 to 50 nm. If the average primary particle size is within this range, there is no particular limitation on the lower limit for the primary particle size of each silica, but the coefficient of variation in the primary particle size distribution is preferably 0.4 or less, more preferably 0.01 to 0.4. When the coefficient of variation is larger than 0.4, the porosity is reduced. If the particle size is within this range, the surface surface is less affected and a higher gloss can be obtained. The coefficient of variation in the primary particle size distribution of silica or the like is determined by observing the cross section or surface of the void layer with an electron microscope, obtaining the particle size of 1000 arbitrary primary particles, and calculating the standard deviation of the particle size distribution as the number average particle size Calculated as the value divided by the value. Here, each particle size is represented by a diameter assuming a circle equal to the projected area.

Alumina or alumina hydrate may be crystalline or amorphous, and any shape such as irregular particles, spherical particles, and acicular particles can be used. In the recording medium, the ratio of the inorganic fine particles to the binder of the porous layer is preferably 2 to 50 times in terms of mass ratio. When the mass ratio is twice or more, the porosity of the porous layer is good, it is easy to obtain a sufficient void volume, and excessive binder can be prevented from swelling and closing the void during ink jet recording. On the other hand, when this ratio is 50 times or less, it is preferable that cracking hardly occurs when the porous layer is applied as a thick film. A particularly preferable ratio of the inorganic fine particles to the binder is 2.5 to 20 times, and 5 to 15 times is more preferable from the viewpoint of resistance to breakage of the dry coating film.

In order to obtain a porous layer having a high porosity, the specific surface area measured by the BET method is preferably 100 m ² / g or more. Moreover, it is preferable that the minimum of a specific surface area is 40 m < ² > / g or more from a viewpoint from which the luster close | similar to a photograph is acquired. The BET method referred to in the present invention is a method for measuring the specific surface area by a method for determining the surface area per 1 g from the gas phase adsorption isotherm.

In particular, the porous layer according to the present invention preferably has a capacity of 15 to 40 ml / m ² per unit area. This capacity refers to the volume of bubbles generated when a unit volume of the coating film is applied to water, the volume of water that can be absorbed by the coating film, or the ink jet recording medium finally obtained. It is defined as the amount of liquid transfer when the contact time is 2 seconds as measured by the liquid absorbency test method (Bristow method) of paper and paperboard specified in TAPPI 51.

<binder>
As the binder for the porous layer, those used as the binder for the surface layer can be used. For example, gelatin, polyvinyl pyrrolidone, pullulan, polyvinyl alcohol or derivatives thereof, polyethylene glycol, hydroxyethyl cellulose, dextran, dextrin, water-soluble Polyvinyl butyral etc. can be mentioned.

<Various additives>
Various additives can be added to the coating solution for forming the porous layer. Such additives include, for example, cationic polymers, crosslinking agents, surfactants (cations, nonions, anions, amphoterics), white background color adjusting agents, fluorescent whitening agents, antifungal agents, viscosity adjusting agents, low boiling points. Examples include organic solvents, high boiling point organic solvents, latex emulsions, anti-fading agents, ultraviolet absorbers, polyvalent metal compounds (water-soluble or water-insoluble), matting agents, silicone oils, etc. Among them, cationic polymers are inorganic. This is particularly preferable because it promotes the dispersion of the fine particles to smooth the porous layer and has the effect of reducing the surface Ra.

  In general, the cationic polymer used in the porous layer according to the present invention may be the same as the cationic polymer described in the surface layer. A preferable cationic polymer is obtained as a homopolymer of the monomer having the quaternary ammonium base, a copolymer with other monomers, or a condensation polymer.

Examples of cationic polymers include polyethyleneimine, polyallylamine, polyvinylamine, dicyandiamide polyalkylene polyamine condensate, polyalkylene polyamine dicyandiamide ammonium salt condensate, dicyandiamide formalin condensate, epichlorohydrin-dialkylamine polycondensate, 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-methacryloyloxy) trimethyl ammonium chloride polymer And dimethylaminoethyl methacrylate polymer.

In the porous layer according to the present invention, a polyvalent metal compound may be used to improve water resistance. For example, it is used in sulfates such as Al ³⁺ and Zr ²⁺ , chlorides, nitrates, acetates and the like. In addition, inorganic polymer compounds such as basic polyaluminum hydroxide and zirconyl acetate are also included as examples of preferable water-soluble polyvalent metal compounds. These water-soluble polyvalent metal ions are generally used in a range of 0.05 to 20 mmol, preferably 0.1 to 10 mmol, per 1 m ^{2 of} recording paper.

  In the porous layer which concerns on the inkjet recording medium of this invention, you may contain the organic polymer which has an epoxy group with a polyvalent metal compound. By using an organic polymer having an epoxy group in the porous layer, the ink absorption rate can be increased. This is because the swelling of polyvinyl alcohol is suppressed by crosslinking, and the ink absorption rate due to the voids is not inhibited.

  Furthermore, in order to prevent cracking during coating production, an amino acid may be contained in addition to the polyvalent metal compound and the organic polymer having an epoxy group.

  The porous layer according to the present invention may contain a compound having a plurality of carbon-carbon unsaturated bonds.

  Specific examples of the compound having a plurality of non-aromatic carbon-carbon unsaturated bonds in the molecule include resins obtained by copolymerizing butadiene alone or other polymerizable monomers, diallyl phthalate resins, unsaturated polyester resins, furans. Resins, resins such as C5 petroleum resin, terpene resin, cyclopentadiene resin, diallyl phthalate, triallyloxy-1,3,5-triazinepentaerythritol tetra (meth) acrylate, trimethylolpropane tri (meth) acrylate, divinyl Examples include polymers having a plurality of polymerizable groups such as benzene, but are not limited to these examples. The molecular weight of the compound having a plurality of carbon-carbon unsaturated bonds is preferably 1000 or more from the viewpoint of odor and the like, and more preferably 10,000 or less from the viewpoint of ink absorbability.

  Among these compounds, a polymer containing a butadiene or isoprene monomer is preferable, and polybutadiene having a terminal modified with a hydroxyl group, a carboxyl group, an amino group, maleic anhydride, or the like, or styrene, acrylonitrile, (meth) acrylic acid. Examples thereof include polybutadiene, polyisoprene and the like copolymerized with an ester, among which polybutadiene or polyisoprene is particularly preferable.

  The ink jet recording medium of the present invention may contain a urea compound in order to further improve cracking during coating and ink absorbability. Specific examples of urea compounds that may be contained include urea, biuret, semicarbazide hydrochloride, biurea, 1-methylurea, 1,1-dimethylurea, 1,3-dimethylurea, 1,1,3-trimethyl. Urea, 1,1,3,3-tetramethylurea, 1-ethylurea, 1,1-diethylurea, 1,3-diethylurea, 1,1,3-triethylurea, 1- (n-propyl) urea 1- (n-butyl) urea, 1- (tert-butyl) urea, 1-allylurea, 1,3-diallylurea, 1-phenylurea, 1,1-diphenylurea, 1,3-diphenylurea, 1- (o-tolyl) urea, 1- (m-tolyl) urea, phenylacetylurea, 1- (benzyl) urea, 1-hydroxyurea, 1,3-bis (trimethylsilyl) urea, bis (pentamethylene) urea , - imidazolone, barbituric acid, 1,3-dicyclohexyl urea, nitrosoureas, di cyan Zia spermidine, hydantoin and the like, may be used in combination of two or more thereof. Of these, urea is preferred.

  In the ink jet recording medium of the present invention, a fluorosurfactant may be contained in any layer in order to adjust the surface tension of the coating solution. The fluorosurfactant may be any of anion type, cation type, nonion type, and betaine type, and may be a low molecule or a polymer. For example, perfluoroalkyl sulfonate, perfluoroalkyl carboxylate, perfluoroalkenyl sulfonate, perfluoroalkenyl carboxylate, perfluoroalkyl ethylene oxide adduct, perfluoroalkenyl polyoxyethylene ether, perfluoroalkyl fourth Examples include quaternary ammonium salts, perfluoroalkenyl quaternary ammonium salts, perfluoroalkylaminosulfonates, perfluoroalkenyl betaines, perfluoroalkyl group-containing oligomers, perfluoroalkyl phosphate esters, etc., selected as appropriate or mixed Can be used.

  Among the above fluorosurfactants, it is preferable to use a cationic fluorosurfactant, a nonionic fluorosurfactant, or a betaine fluorosurfactant.

  The porous layer may contain a volatile acid or a salt thereof and a water-soluble polyvalent metal compound. By using a volatile acid or a salt thereof in the porous layer, the pH of the porous layer coating solution can be preferably adjusted. The volatile acid means an acid that volatilizes easily with moisture and volatilizes without being decomposed at normal pressure. Specific examples include lower fatty acids having 10 or less carbon atoms such as hydrochloric acid, nitric acid, hydrofluoric acid, carbonic acid, and acetic acid. Among these, carbonic acid and acetic acid are preferable from the viewpoints of volatility, acidity, handleability, and the like.

  In the present invention, the volatile acid may be used in the form of a salt with a cationic compound. Specific examples include salts with alkali metal ions such as sodium ion, potassium ion and lithium ion, salts with alkaline earth metal ions such as magnesium ion, calcium ion and barium ion, aluminum ion, zirconium ion and zinc ion. Salts with metal ions and complex ions containing these metal ions, salts with inorganic or organic ammonium ions such as triethanolammonium ion and pyridinium ion, salts with other organic compounds and polymers having a cationic group, etc. Is mentioned.

  The porous layer according to the present invention may be a single layer or a multilayer. In the case of a multilayer configuration, it is preferable to apply all the layers simultaneously from the viewpoint of reducing manufacturing costs.

(Swelling layer)
The swelling type solvent absorbing layer needs to have a swelling layer exhibiting a high swelling property with respect to ink droplets. In this swelling layer, a hydrophilic binder exhibiting ink liquid swellability is used as a main component of the swelling layer. Examples of hydrophilic binders preferably used include gelatin or gelatin derivatives, polyvinyl pyrrolidone (average molecular weight is preferably about 200,000 or more), pullulan, polyvinyl alcohol or derivatives thereof, polyethylene glycol (average molecular weight is preferably 100,000 or more). Carboxymethyl cellulose, hydroxyethyl cellulose, dextran, dextrin, polyacrylic acid and salts thereof, agar, κ-carrageenan, λ-carrageenan, ι-carrageenan, xanthene gum, locust bean gum, alginic acid, gum arabic, JP-A-7-195826 And polyalkylene oxide copolymerizable polymers described in JP-A-7-9757, water-soluble polyvinyl butyral, or carboxyl groups described in JP-A-62-245260 It can be mentioned polymers such as a copolymer having repeat alone or of these vinyl monomers vinyl monomer having a sulfonic acid group. These hydrophilic binders may be used alone or in combination of two or more.

  The effect of the present invention can be sufficiently obtained by using both a porous layer and a swollen layer as the solvent absorption layer. However, since the porous layer has a higher solvent absorption rate, it is porous from the viewpoint of ink overflow. A layer is preferred.

  The film surface pH of the recording medium used in the present invention is preferably 3 to 10. As a result, the pigment in the ink is less likely to agglomerate, and the density and saturation can be improved. The film surface pH of the recording medium can be adjusted using various known additives such as a pH adjusting agent. In the present invention, the film surface pH of the recording medium is determined by dropping 0.05 ml of pure water onto the solvent absorption layer of the recording medium and measuring the pH.

[Support]
As the support used for the ink jet recording medium of the present invention, a water-absorbing support (for example, paper) or a non-water-absorbing support can be used. From the viewpoint of obtaining a higher-quality print, non-water-absorbing support is possible. An ionic support is preferred.

  As the non-water-absorbing support preferably used, for example, polyester film, diacetate film, triatesate film, polyolefin film, acrylic film, polycarbonate film, polyvinyl chloride film, polyimide film, cellophane, Examples thereof include a transparent or opaque film made of a material such as celluloid, or a resin-coated paper in which both surfaces of a base paper are coated with a polyolefin resin coating layer, so-called resin-coated paper. Particularly preferred is resin-coated paper.

  When applying the water-soluble coating solution on the support, the support is subjected to corona discharge treatment, subbing treatment or the like for the purpose of increasing the adhesive strength between the surface and the coating layer. Is preferred. Furthermore, the inkjet recording medium of the present invention may be a colored support.

  The resin-coated paper laminated with polyethylene, which is the most preferred representative of polyolefin, will be described below.

  The base paper used for the resin-coated paper is made from wood pulp as a main raw material and, if necessary, paper making using synthetic pulp such as polypropylene or synthetic fibers such as nylon or polyester in addition to wood pulp. As wood pulp, for example, any of LBKP, LBSP, NBKP, NBSP, LDP, NDP, LUKP, NUKP can be used, but more LBKP, NBSP, LBSP, NDP, LDP with more short fibers are used. Is preferred. However, the ratio of LBSP or LDP is preferably 10 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 quaternary ammonium, and the like can be appropriately added.

  The freeness of the pulp used for papermaking is preferably 200 to 500 ml as defined by CSF, and the fiber length after beating is a 24 mesh residual mass% defined by JIS-P-8207, and 42 30-70 mass% of sum with the mass% of a mesh remainder is preferable. 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 a high smoothness by subjecting it to a calendar process 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 (according to the method defined in 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, the same sizing agents 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 a 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) or high-density polyethylene (HDPE), but some other LLDPE, polypropylene, etc. can also be used.

  The layer on the coated layer side is preferably one in which rutile or anatase type titanium oxide is added to polyethylene to improve opacity and whiteness, as is widely done in photographic paper. The titanium oxide content is 1 to 20% by mass, preferably 2 to 15% by mass, based on polyethylene.

  The polyethylene-coated paper can be used as glossy paper, or when the polyethylene is melt-extruded and coated on the surface of the base paper, a matte surface or silk-like surface obtained by ordinary photographic photographic paper by performing a so-called molding process Those having a fine grain surface can also be used in the present invention.

  The amount of polyethylene used on the front and back of the base paper is selected so as to optimize the film thickness of the coating composition and the curl at low humidity and high humidity after providing the back layer, but the coating composition according to the present invention It is preferable that the polyethylene layer on the side to be coated is 20 to 40 μm, and the back layer side is 10 to 30 μm.

  Furthermore, the polyethylene-coated paper support preferably has the following characteristics.

1) Tensile strength: strength specified by JIS-P-8113, preferably 20-300N in the vertical direction and 10-200N in the horizontal direction 2) Tear strength: as defined by JIS-P-8116 The longitudinal direction is preferably 0.1 to 2N and the lateral direction is preferably 0.2 to 2N. 3) Compression elastic modulus: ≧ 1030 N / cm ²
4) Surface Beck smoothness: 500 seconds or more is preferable as a glossy surface under the conditions specified in JIS-P-8119, but may be less than this for so-called molded products. 5) Back surface Beck smoothness: JIS- 100 to 800 seconds are preferable under the conditions specified in P-8119. 6) Opacity: Transmittance of light in the visible range is 20% or less, particularly 15% under the measurement conditions of linear light incidence / diffuse light transmission conditions. 7) Whiteness: Hunter whiteness as defined in JIS-P-8123, preferably 90% or more. Further, when measured by JIS-Z-8722 (non-fluorescent) and JIS-Z-8717 (containing fluorescent agent) and displayed by the color display method defined in JIS-Z-8730, L ^* = 90 to 98, a ^* = − 5 to +5, b ^* = − 10 to +5 are preferable.

An undercoat layer is preferably provided on the solvent absorption layer (porous layer) side of the support for the purpose of improving the adhesion with the solvent absorption layer. The binder for the undercoat layer is preferably a hydrophilic polymer such as gelatin or polyvinyl alcohol, or a latex polymer having a Tg of −30 to 60 ° C. These binders are used in the range of 0.001 to ² g per 1 m ^{2 of} the ink jet recording medium. In the undercoat layer, a small amount of a conventionally known antistatic agent such as a cationic polymer can be contained for the purpose of antistatic.

[Back layer]
A back layer may be provided on the surface of the support opposite to the porous layer side for the purpose of improving slipperiness and charging characteristics. The binder for the back layer is preferably a hydrophilic polymer such as gelatin or polyvinyl alcohol, a latex polymer having a Tg of −30 to 60 ° C., an antistatic agent such as a cationic polymer, various surfactants, and an average. A matting agent having a particle size of about 0.5 to 20 μm can also be added. The thickness of the back layer is generally 0.1 to 1 μm, but in the case where the back layer is provided for preventing curling, it is generally in the range of 1 to 20 μm. The back layer may be composed of two or more layers.

  In coating the back layer, it is preferable to use a surface treatment such as corona treatment or plasma treatment on the support surface.

[Method for producing inkjet recording medium]
The coating method of each coating solution can be appropriately selected from known methods. For example, gravure coating method, roll coating method, rod bar coating method, air knife coating method, spray coating method, extrusion coating method, curtain A coating method or an extrusion coating method using a hopper described in US Pat. No. 2,681,294 is preferably used.

〔ink〕
In the inkjet recording method of the present invention, an image containing at least a water-soluble solvent and a color material is ejected onto the inkjet recording medium of the present invention to form an image.

  In the present invention, a pigment ink is used as a colorant, which is particularly preferable from the viewpoint of image storage stability. As the pigment used in the pigment ink, insoluble pigments, organic pigments such as lake pigments, carbon black and the like can be preferably used.

  The insoluble pigment is not particularly limited. Dioxazine, thiazole, phthalocyanine, diketopyrrolopyrrole and the like are preferable.

  Specific pigments that can be preferably used include the following pigments.

  Examples of the magenta or red pigment include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. And CI Pigment Red 222.

  Examples of the pigment for orange or yellow include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. And CI Pigment Yellow 138.

  Examples of the pigment for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. And CI Pigment Green 7.

  For these pigments, a pigment dispersant may be used as necessary. Examples of pigment dispersants that can be used include higher fatty acid salts, alkyl sulfates, alkyl ester sulfates, alkyl sulfonates, sulfosuccinates. Acid salt, naphthalene sulfonate, alkyl phosphate, polyoxyalkylene alkyl ether phosphate, polyoxyalkylene alkyl phenyl ether, polyoxyethylene polyoxypropylene glycol, glycerin ester, sorbitan ester, polyoxyethylene fatty acid amide, amine Activators such as oxides, or styrene, styrene derivatives, vinyl naphthalene derivatives, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itaconic acid, itaconic acid derivatives, fumaric acid, fumaric acid derivatives Block copolymer comprising a monomer of the above, may be mentioned random copolymers and salts thereof.

  As a method for dispersing the pigment, various dispersing machines such as a ball mill, a sand mill, an attritor, a roll mill, an agitator, a Henschel mixer, a colloid mill, an ultrasonic homogenizer, a pearl mill, a wet jet mill, and a paint shaker can be used. It is also preferable to use a centrifugal separator or a filter for the purpose of removing the coarse particles of the pigment dispersion.

  The average particle size of the pigment particles in the pigment ink is selected in consideration of stability in the ink, image density, glossiness, light resistance, etc. In addition, the image forming method of the present invention improves glossiness, textures. It is preferable to select the particle size as appropriate from the viewpoint of improvement. In the present invention, the reason for improving the glossiness or texture is not clear at this stage, but in the formed image, the pigment is in a desirable state dispersed in the film in which the thermoplastic resin is melted. I guess it is related. For the purpose of high-speed processing, the thermoplastic resin must be melted and formed into a film in a short time, and the pigment must be sufficiently dispersed in the film. At this time, it is considered that the surface area of the pigment has a great influence, and therefore there is an optimum region for the average particle diameter.

  The water-based ink composition which is a preferable form as the pigment ink preferably uses a water-soluble organic solvent in combination. Examples of the water-soluble organic solvent that can be used in the present invention include alcohols (for example, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, secondary butanol, tertiary butanol, pentanol, hexanol, cyclohexanol, benzyl). Alcohol), polyhydric alcohols (for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, thiodiglycol Etc.), polyhydric alcohol ethers (for example, ethylene glycol monomethyl ether, ethylene glycol) Ether monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether , Triethylene glycol monobutyl ether, ethylene glycol monophenyl ether, propylene glycol monophenyl ether, etc.), amines (for example, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, mole) Phosphorus, N-ethylmorpholine, ethylenediamine, diethylenediamine, triethylenetetramine, tetraethylenepentamine, polyethyleneimine, pentamethyldiethylenetriamine, tetramethylpropylenediamine, etc.), amides (eg, formamide, N, N-dimethylformamide, N , N-dimethylacetamide, etc.), heterocyclic rings (for example, 2-pyrrolidone, N-methyl-2-pyrrolidone, cyclohexylpyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, etc.), sulfoxides ( For example, dimethyl sulfoxide etc.), sulfones (for example, sulfolane etc.), urea, acetonitrile, acetone etc. are mentioned. Preferable water-soluble organic solvents include polyhydric alcohols. Furthermore, it is particularly preferable to use a polyhydric alcohol and a polyhydric alcohol ether in combination.

  One or more water-soluble organic solvents may be used in combination. The total amount of the water-soluble organic solvent added to the ink is 5 to 60% by mass, preferably 10 to 35% by mass.

  The ink composition may be prepared by adding various known additives such as viscosity according to the purpose of improving ejection stability, print head and ink cartridge compatibility, storage stability, image storage stability, and other various performances as necessary. Adjusting agents, surface tension adjusting agents, specific resistance adjusting agents, film forming agents, dispersants, surfactants, ultraviolet absorbers, antioxidants, anti-fading agents, anti-fouling agents, rust inhibitors, etc. are appropriately selected and used. For example, polystyrene, polyacrylic acid esters, polymethacrylic acid esters, polyacrylamides, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, or a copolymer thereof, urea resin, melamine resin, etc. Organic latex fine particles, liquid paraffin, dioctyl phthalate, tricresyl phosphate, silicone oil and other oil droplet fine particles, Various surfactants of thione or nonion, ultraviolet absorbers described in JP-A-57-74193, JP-A-57-87988 and JP-A-62-261476, JP-A-57-74192, JP-A-57-87989, 60-72785, 61-146591, anti-fading agents described in JP-A-1-95091 and 3-13376, JP-A-59-42993, 59-52689, 62- 280069, 61-242871, and JP-A-4-219266, etc., optical brighteners, pH adjusters such as sulfuric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate, etc. Can be mentioned.

  The ink has a viscosity at the time of flight of preferably 40 mPa · s or less, and more preferably 30 mPa · s or less. The ink composition has a surface tension during flight of preferably 20 mN / m or more, and more preferably 30 to 45 mN / m.

  According to the ink jet recording method of the present invention, an image having a uniform gloss on the white background and the image portion, rich gradation, and good storability can be obtained regardless of variations in the pigment ink.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. Unless otherwise specified, “%” in the examples represents “mass%”.

<< Preparation of surface layer coating liquid >>
(Preparation of surface layer coating solution 1)
To 400 g of uniformly dispersed titanium oxide aqueous dispersion (TSK-5, solid content 30%, manufactured by Ishihara Sangyo Co., Ltd.), 26% by mass of polyaluminum hydroxide (manufactured by Taki Chemical Co., Ltd.) 50 g of Takebine # 1500) was added with stirring at 3000 rpm at room temperature.

  Next, after stirring at 40 ° C., 500 g of the above dispersion was mixed with 250 g of an aqueous 8% by weight polyvinyl alcohol (manufactured by Kuraray, PVA224) at a polymerization degree of 2400, and the pH was adjusted to 4.5. Finally, the total amount was adjusted to 1000 g with pure water to prepare a surface layer coating solution 1.

(Preparation of surface layer coating solution 2)
Silica dispersion (pH 2.6, ethanol 0.5% by mass) containing 30% by mass of gas phase method silica (Nippon Aerosil Co., Ltd .; Aerosil 300) having an average particle size of primary particles uniformly dispersed in advance of about 7 nm Containing) and 267 g of a titanium oxide aqueous dispersion (TSK-5, solid content 30%, manufactured by Ishihara Sangyo Co., Ltd.) and then stirring, 26 mass% polyaluminum hydroxide (Taki) 50 g of Takebayine # 1500 manufactured by Chemical Industry Co., Ltd. was added at room temperature.

  Subsequently, 0.5 mm zirconia beads were added, sand mill dispersion was performed, zirconia beads were removed by filtration, and the whole amount was finished with pure water so that the total content of inorganic fine particles became 20% by mass.

  Next, after stirring at 40 ° C., 500 g of the dispersion was mixed with 250 g of an aqueous 8% by weight polyvinyl alcohol (manufactured by Kuraray, PVA224) at a polymerization degree of 2400, and the pH was adjusted to 4.2. Finally, the total amount was adjusted to 1000 g with pure water to prepare a surface layer coating solution 2.

(Preparation of surface layer coating solutions 2A and 2B)
Surface layer coating solutions 2A and 2B were prepared in the same manner as in the preparation of the surface layer coating solution 2, except that the pH was changed from 4.2 to pH 5.0 and pH 6.0, respectively.

(Preparation of surface layer coating solutions 3 to 8)
In the preparation of the surface layer coating solution 2, surface layer coating solutions 3 to 8 were prepared in the same manner except that the type of cationic substance, the type of inorganic fine particles and the mixing ratio were changed as shown in Table 1.

  The total amount of the cationic substance and the inorganic fine particles was the same as that of the surface layer coating solution 2.

  In addition, the detail of each additive used for preparation of the said surface layer coating liquids 1-8 of Table 1 is as follows.

<Cationic substance>
PAC: polyaluminum hydroxide (manufactured by Taki Chemical Industry Co., Ltd., Takebine # 1500)
PAA: polyallylamine hydrochloride (manufactured by Nittobo Co., Ltd., PAA-HCl-03)

<Inorganic fine particles>
TiO ₂ : Titanium oxide (manufactured by Ishihara Sangyo Co., Ltd., TSK-5)
SiO ₂ : Gas phase method silica (produced by Nippon Aerosil Co., Ltd., Aerosil 300)
ZrO ₂ : Zirconium oxide (Zircosol ZC-2, manufactured by Daiichi Elemental Chemical Co., Ltd.)
CoSi: Colloidal silica (manufactured by Nissan Chemical Industries, Snowtex AK-L)
<< Preparation of solvent absorption layer coating liquid >>
(Preparation of solvent absorption layer coating solution 1)
The average particle diameter of primary particles uniformly dispersed in advance in 120 g of 10% by weight of an aqueous cationic polymer P-1 solution (containing 10% by weight of n-propanol and 2% by weight of ethanol) is about 7 nm. 400 g of silica dispersion (pH 2.6, containing 0.5% by mass of ethanol) containing 30% by mass of phase method silica (Aerosil 300 manufactured by Nippon Aerosil Co., Ltd.), 3.6 g of boric acid, borax 0.8 g was added with stirring at 3000 rpm at room temperature.

  Subsequently, 0.5 mm zirconia beads were added, sand mill dispersion was performed, zirconia beads were removed by filtration, and the whole amount was finished with pure water so that the content of inorganic fine particles was 20% by mass to prepare a dispersion.

  Next, after stirring at 40 ° C., 500 g of the dispersion was mixed with 250 g of an aqueous 8% by weight polyvinyl alcohol (manufactured by Kuraray, PVA224) at a polymerization degree of 2400, and the pH was adjusted to 6.2. Finally, the total amount was adjusted to 1000 g with pure water to prepare a solvent absorption layer coating solution 1.

(Preparation of solvent absorption layer coating solution 2)
Gas phase method silica (manufactured by Nippon Aerosil Co., Ltd.) having an average particle size of about 7 nm of primary particles uniformly dispersed in advance in 120 g of 8% by mass of an anionic polymer dispersant (John Crill 70 manufactured by Johnson Polymer Co., Ltd.) , 400 g of silica dispersion containing 30% by mass of Aerosil 300) (pH 2.6 and 0.5% by mass of ethanol), 3.6 g of boric acid and 0.8 g of borax at 3000 rpm at room temperature. Added with stirring.

  Subsequently, 0.5 mm zirconia beads were added, sand mill dispersion was performed, zirconia beads were removed by filtration, and the whole amount was finished with pure water so that the content of inorganic fine particles was 20% by mass to prepare a dispersion.

  Next, after stirring at 40 ° C., 500 g of the dispersion was mixed with 250 g of an aqueous 8% by weight polyvinyl alcohol (manufactured by Kuraray, PVA224) at a polymerization degree of 2400, and the pH was adjusted to 6.2. Finally, the total amount was adjusted to 1000 g with pure water to prepare a solvent absorption layer coating solution 2.

(Preparation of solvent absorption layer coating solution 3)
<Preparation of alumina dispersion>
Alumina hydrate (Sasole, Dispersal HP18) 0.50kg
10L of pure water
1 mol / L hydrochloric acid was added to the alumina dispersion to adjust the pH to 4.0, and the mixture was stirred at 95 ° C. for 2 hours. Subsequently, 1 mol / L sodium hydroxide aqueous solution was added, pH was adjusted to 10.0, and also it stirred for 8 hours. After stirring, the mixture was cooled to room temperature, the pH was adjusted to 7-8, desalted, and acetic acid was further added for peptization. After concentrating until the solid content becomes 17%, a 9% aqueous solution of polyvinyl alcohol (PVA117, manufactured by Kuraray Industries Co., Ltd.) is mixed and mixed so that the solid content ratio of alumina and polyvinyl alcohol is 10: 1 by mass ratio. By stirring, a solvent absorption layer coating solution 3 was obtained.

(Preparation of solvent absorption layer coating solution 4)
The following additives were stirred and mixed to prepare a solvent absorption layer coating solution 4.

800ml of pure water
40 g of phenylcarbamoylated gelatin (amino group blocking ratio = about 88%)
Polyvinylpyrrolidone (K-90) 25g
Polyethylene oxide (average molecular weight about 100,000) 12g
Surfactant-2 0.7g
Surfactant-3 0.3g
Hardener-1 2.1g
Each solvent absorption layer coating solution prepared as described above was filtered through a 20 μm-capable filter.

<Production of recording medium>
[Production of Recording Medium 101]
170 g / m ² of polyethylene-coated paper both sides of the base paper coated with polyethylene (the polyethylene coating layer of the image recording layer side contained 8% of anatase type titanium oxide, likewise the image recording layer side to the 0.05 g / m ² The surface layer coating solution 1 prepared above using a wire bar on the opposite side, and having a back layer containing 0.2 g / m ² of latex having a Tg of about 80 ° C. The recording medium 101 having only the surface layer was produced by applying and drying under the condition that the amount applied with drying was 3.2 g / m ² .

[Production of recording media 102 to 106]
In the production of the recording medium 101, the recording media 102 to 106 were produced in the same manner except that the surface layer coating solutions 2 to 6 were used instead of the surface layer coating solution 1.

[Production of Recording Medium 107]
170 g / m ² of polyethylene-coated paper both sides of the base paper coated with polyethylene (the polyethylene coating layer of the image recording layer side contained 8% of anatase type titanium oxide, likewise the image recording layer side to the 0.05 g / m ² A solvent-absorbing layer prepared as a lower layer using a die coater on the opposite side, and having a back layer containing 0.2 g / m ² of latex having a Tg of about 80 ° C. The surface layer coating solution 1 prepared above is coated and dried simultaneously under the condition that the coating solution 1 has a dry weight of 30 g / m ² and the dry coating amount of 3.2 g / m ^2. Thus, a recording medium 107 having two layers was produced.

[Preparation of recording media 108 to 119]
Recording media 108 to 119 were produced in the same manner as in the production of the recording medium 107 except that the types of the solvent absorption layer coating liquid and the surface layer coating liquid were changed to the combinations shown in Table 1.

[Production of Recording Medium 120]
170 g / m ² of polyethylene-coated paper both sides of the base paper coated with polyethylene (the polyethylene coating layer of the image recording layer side contained 8% of anatase type titanium oxide, likewise the image recording layer side to the 0.05 g / m ² And the other side has a back layer containing 0.2 g / m ² of latex having a Tg of about 80 ° C.), using the die coater, the solvent absorbing layer coating solution prepared above A recording medium 120 having only a solvent absorption layer was produced by applying and drying 1 as a single layer under the condition that 1 was 30 g / m ² .

(Measurement of hydrogen bonding components)
For each surface layer of each recording medium produced above, the contact angle with respect to nonane, propylene carbonate, and water on the surface of the recording medium at 100 ms was measured using a contact angle measuring machine (CA-VP manufactured by Kyowa Interface Science Co., Ltd.). The value was calculated according to the method described in the literature (J. PANZER, Journal of Colloid and Interface Science, Vol 44, No. 1, 1974) to obtain the hydrogen bonding component on the surface of the recording medium.

[Measurement of average refractive index n]
Using the known refractive index of each inorganic compound used in the surface layer, the average refractive index n was calculated according to the mixing ratio in the surface layer.

[Measurement of 60 degree gloss]
The image forming side surface of each recording medium was measured for 60 ° glossiness according to JIS-Z-8741 using a variable angle gloss meter (VGS-1001DP) manufactured by Nippon Denshoku Industries Co., Ltd.

[Measurement of centerline surface roughness Ra]
According to the method prescribed in JIS B 0601, the surface on the image forming side of each recording medium is RST / PLUS made by WYKO, the surface is the objective lens 10 times, the internal lens is 0.5 times, the center line surface The roughness Ra was measured.

  The results obtained as described above are shown in Table 1.

<Preparation of ink set>
[Preparation of color ink set]
(Preparation of pigment dispersion)
<Preparation of Yellow Pigment Dispersion 1>
C. I. Pigment Yellow 128 20% by mass
Styrene-acrylic acid copolymer (molecular weight 10,000, acid value 120) 12% by mass
Diethylene glycol 15% by mass
Ion-exchanged water 53% by mass
The above additives were mixed and dispersed using a horizontal bead mill (System Zetamini manufactured by Ashizawa Co., Ltd.) filled with 60% by volume of 0.3 mm zirconia beads to obtain Yellow Pigment Dispersion 1. The average particle size of the obtained yellow pigment was 112 nm.

<Preparation of magenta pigment dispersion>
C. I. Pigment Red 122 25% by mass
Jonkrill 61 (acrylic-styrene resin, manufactured by Johnson Polymer)
18% by mass in solid content
Diethylene glycol 15% by mass
Ion-exchanged water 42% by mass
The above additives were mixed and dispersed using a horizontal bead mill (System Zeta Mini manufactured by Ashizawa Co., Ltd.) filled with 0.3 mm zirconia beads at a volume ratio of 60% to obtain a magenta pigment dispersion 1. The average particle size of the obtained magenta pigment was 105 nm.

<Preparation of Cyan Pigment Dispersion 1>
C. I. Pigment Blue 15: 3 25% by mass
Jonkrill 61 (acrylic-styrene resin, manufactured by Johnson Polymer)
15% by mass in solid content
Glycerin 10% by mass
Ion-exchanged water 50% by mass
The above additives were mixed and dispersed using a horizontal bead mill (System Zetamini manufactured by Ashizawa Co., Ltd.) filled with 60% by volume of 0.3 mm zirconia beads to obtain cyan pigment dispersion 1. The average particle diameter of the obtained cyan pigment was 87 nm.

<Preparation of Black Pigment Dispersion 1>
Carbon black 20% by mass
Styrene-acrylic acid copolymer (molecular weight 7000, acid value 150) 10% by mass
Glycerin 10% by mass
Ion exchange water 60% by mass
The above additives were mixed and dispersed using a horizontal bead mill (System Zeta Mini manufactured by Ashizawa Co., Ltd.) filled with 0.3% zirconia beads at a volume ratio of 60% to obtain a black pigment dispersion 1. The average particle size of the obtained black pigment was 75 nm.

(Preparation of pigment ink)
<Preparation of yellow dark ink 1>
Yellow pigment dispersion 1 25% by mass
20% by mass of ethylene glycol
Diethylene glycol 10% by mass
Surfactant (Surfinol 465 Nissin Chemical Industry Co., Ltd.) 0.1% by mass
Ion-exchanged water 44.9% by mass
Each of the above compositions was mixed and stirred, and filtered through a 1 μm filter to prepare yellow dark ink 1. The average particle diameter of the pigment in the yellow dark ink 1 was 120 nm, and the surface tension was 36 mN / m.

<Preparation of magenta dark ink 1>
Magenta pigment dispersion 1 25% by mass
Ethylene glycol 15% by mass
Diethylene glycol 20% by mass
Surfactant (Surfinol 465, Nissin Chemical Industry Co., Ltd.) 0.1% by mass
Ion-exchanged water 54.9% by mass
The above compositions were mixed and stirred, and filtered through a 1 μm filter to prepare magenta dark ink 1. The average particle size of the pigment in the magenta dark ink 1 was 113 nm, and the surface tension was 35 mN / m.

<Preparation of magenta light ink 1>
Magenta pigment dispersion 1 3% by mass
Ethylene glycol 25% by mass
Diethylene glycol 10% by mass
Surfactant (Surfinol 465, Nissin Chemical Industry Co., Ltd.) 0.1% by mass
Ion-exchanged water 61.9% by mass
The above compositions were mixed and stirred, and filtered through a 1 μm filter to prepare magenta light ink 1. The average particle diameter of the pigment in the magenta light ink 1 was 110 nm, and the surface tension was 37 mN / m.

<Preparation of cyan dark ink 1>
Cyan pigment dispersion 1 10% by mass
20% by mass of ethylene glycol
Diethylene glycol 10% by mass
Surfactant (Surfinol 465, Nissin Chemical Industry Co., Ltd.) 0.1% by mass
Ion-exchanged water 59.9% by mass
The above compositions were mixed and stirred, and filtered through a 1 μm filter to prepare cyan dark ink 1. The average particle size of the pigment in cyan dark ink 1 was 95 nm, and the surface tension was 36 mN / m.

<Preparation of cyan light ink 1>
Cyan pigment dispersion 1 2% by mass
Ethylene glycol 25% by mass
Diethylene glycol 10% by mass
Surfactant (Surfinol 465, Nissin Chemical Industry Co., Ltd.) 0.2% by mass
Ion-exchanged water 62.8% by mass
The above compositions were mixed and stirred, and filtered through a 1 μm filter to prepare cyan light ink 1. The average particle size of the pigment in cyan light ink 1 was 92 nm, and the surface tension was 33 mN / m.

<Preparation of black dark ink 1>
Black pigment dispersion 1 20% by mass
20% by mass of ethylene glycol
Diethylene glycol 10% by mass
Surfactant (Surfinol 465, Nissin Chemical Industry Co., Ltd.) 0.1% by mass
Ion-exchanged water 49.9% by mass
Each of the above compositions was mixed and stirred and filtered through a 1 μm filter to prepare a dark black ink 1. The average particle diameter of the pigment in the black dark ink 1 was 85 nm, and the surface tension was 35 mN / m.

[Preparation of magenta ink set]
(Preparation of magenta ink M1)
Magenta pigment dispersion 1 25% by mass
Ethylene glycol 15% by mass
Diethylene glycol 20% by mass
Ion-exchanged water 55% by mass
The above compositions were mixed, stirred, and filtered through a 1 μm filter to prepare magenta ink M1. The average particle diameter of the pigment in the magenta ink M1 was 116 nm, and the surface tension was 45 mN / m.

(Magenta ink M2)
The magenta dark ink 1 of the color ink set was designated as magenta ink M2. The average particle size of the pigment in the magenta ink M2 was 113 nm, and the surface tension was 35 mN / m.

(Preparation of magenta ink M3)
Magenta pigment dispersion 1 25% by mass
Diethylene glycol 20% by mass
1,2-hexanediol 15% by mass
Surfactant (Surfinol 465, Nissin Chemical Industry Co., Ltd.) 0.1% by mass
Ion-exchanged water 54.9% by mass
The above compositions were mixed, stirred, and filtered through a 1 μm filter to prepare magenta ink M3. The average particle size of the pigment in the magenta ink M3 was 115 nm, and the surface tension was 27 mN / m.

<< Inkjet image recording and evaluation >>
Image recording and evaluation were performed according to the following method using the recording medium prepared above and a color ink set or a magenta ink set.

[Inkjet image recording]
<Image recording 1>
Each of the color inks prepared above is packed in an ink cartridge and mounted on an ink jet printer MC2000 (manufactured by Seiko Epson). Each of the produced recording media is a high-definition color digital issued by the Japan Standards Association. Standard image data “Bride” was printed, and images 1 to 20 were created. Each image was dried for 1 hour in an environment of 23 ° C. and 55% RH. Each recording medium was printed using what was stored at 23 ° C. for one day.

<Image recording 2>
The magenta inks M1, M2, and M3 having different surface tensions of the inks prepared above were loaded into an ink jet printer CL750 (manufactured by Seiko Epson Corporation) black ink cartridge, and each ink was printed on each recording medium. A magenta patch image was output at an output of 10% with the magenta ink.

[Evaluation of recorded images]
(Evaluation of glossiness)
The glossiness of the high-definition color digital standard image data “Bride” created in the image record 1 was evaluated by 20 observers according to the following criteria, and the one with the highest rank was adopted.

A: Glossiness is felt at all color densities in the image area. B: Glossiness is slightly lacking at high image density portions of green and red.

Δ: Glossiness is lacking at high image density areas of yellow, magenta, cyan, and black. ×: No glossiness at all density of all colors (Evaluation of gloss uniformity)
A high-definition color digital standard image data “Bride” created in the above image record 1 is visually evaluated by 15 people to determine whether the white portion of the dress of the bride and the image portion of the other dress color can be distinguished, and the gloss is uniform according to the following criteria Sexuality was evaluated.

◎: There are no people who feel that there is a difference in gloss ○: 1, 2 people who feel that there is a difference in gloss △: 3-10 people who feel that there is a difference in gloss ×: There is a difference in gloss The number of people who felt there was 11-15 people (Evaluation of dot diameter stability)
With respect to 50 non-overlapping dots in the magenta patch image created in the recorded image 2, the major axis length (μm) of the dots is measured using an optical microscope, and the major axis lengths of the magenta ink M1 and the magenta ink M3 are measured. The ratio (M3 / M1) was determined and used as a measure of dot diameter stability.

(Evaluation of ink overflow resistance)
The image of the high-definition color digital standard image data “Bride” created in the image recording 1 was visually observed for the occurrence of bleeding, and ink overflow resistance was evaluated according to the following criteria.

A: Ink overflow is not observed at all. O: Ink overflow is slightly present but no effect on the image quality is observed. Δ: The ink is slightly overflowed and the image quality is slightly deteriorated. X: Ink Is violently overflowing and the image is clearly deteriorated when dripping (Evaluation of water resistance)
Each recording medium on which an image has been formed is immersed in pure water at 25 ° C. for 90 minutes, and then left to stand for 2 days to dry naturally. This operation is repeated up to 5 times in accordance with this, and each time the film is peeled off. Visual observation was performed and water resistance was evaluated according to the following criteria.

○: Even if the above operation is repeated up to the fifth time, no film peeling is observed. Δ: The film peeling occurs in the repeated immersion up to the second to fourth times. ×: The film peeling occurs immediately in the first immersion. (Evaluation of bending resistance)
Each unprinted recording medium was stored for 24 hours in an environment of 23 ° C. and 20% RH, and then placed on a cylindrical aluminum roller of 5, 10, 15, 20, 25, 30, 35, 40, 45, 50 mm. The roll was wound so that the image recording surface was on the outside, the roller diameter at which cracks began to occur on the image recording surface was determined, and bending resistance was evaluated according to the following criteria.

◎: No crack is observed even with a 5 mm roller. ○: The cracked roller diameter is 5 mm or more and 15 mm or less. △: The cracked roller diameter is 20 mm or more and 35 mm or less. Roller diameter is 40 mm or more (Evaluation of scratch resistance)
The image surface of the high-definition color digital standard image data “Bride” created in the above image record 1 is rubbed 5 times with Kimwipe S-200 (manufactured by Crecia), and the presence or absence of surface scratches and the color fading of the image A visual evaluation was performed, and the scratch resistance was evaluated according to the following criteria.

○: Neither scratches nor color fading is observed △: Scratches are slightly generated and some color fading is observed ×: The evaluation results obtained by the above are obvious the occurrence of scratches and severe color fading Is shown in Table 2.

  As is apparent from the results shown in Table 2, the surface layer contains inorganic fine particles having an average refractive index of 2.1 to 2.9 and a binder, and the hydrogen bonding component of the surface tension of the surface is 25 to 50 mN / m. The image formed using the recording medium of the present invention having the above has excellent glossiness, gloss uniformity, dot diameter stability, ink overflow resistance, water resistance, bending resistance and scratch resistance compared to the comparative example. I understand.

Claims (9)

It has a surface layer containing inorganic fine particles having an average refractive index of 2.1 to 2.9 and a binder on the support, and the hydrogen bond component of the surface tension in the surface layer is 25 to 50 mN / m. An inkjet recording medium characterized by the above. 2. The ink jet recording medium according to claim 1, wherein a product S of a center line surface roughness Ra (μm) of the surface layer and an average refractive index of the inorganic fine particles is 1.7 μm or less. The ink jet recording medium according to claim 1, wherein the surface layer contains a hydrogen bonding cationic substance. The inorganic fine particles contained in the surface layer are at least one selected from titanium oxide, cerium oxide, and zirconium oxide, and silica or alumina. Inkjet recording medium. The inkjet recording medium according to any one of claims 1 to 4, further comprising a solvent absorption layer between the surface layer and the support. 6. The solvent absorbing layer is a porous layer containing inorganic fine particles having an average refractive index of 1.3 to 1.7 and an average particle diameter of 1 to 200 nm and a binder. 2. An ink jet recording medium according to 1. The inkjet recording medium according to claim 6, wherein the porous layer is cationic. The inkjet recording medium according to claim 1, wherein the support is resin-coated paper. An ink jet recording method comprising recording an image by ejecting an ink containing at least a water-soluble solvent and a pigment onto the ink jet recording medium according to claim 1.