JP2005246675A - Inkjet recording medium and inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording medium in pigment ink, with which an uniform lustrous feeling is obtained over a white ground and an image part under the condition being printed with the pigment ink and, at the same time, which has a high scratch resistance and with which an image inconsicuous even as scratched is obtained, and an inkjet recording method. <P>SOLUTION: In the inkjet recording medium having a surface layer including fine inorganic particles having an average refractive index of 2.1-2.9 and a binder and a porous layer including a vapor phase method silica having a lone silanol group ratio of 5.0-7.0 and a polyvinyl alcohol on a support, the void volume ratio of the porous layer is at least 60%. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an inkjet recording medium and an inkjet recording method.

  In recent years, with the widespread use of digital cameras or computers, hard copy image recording technology for recording these images on paper or the like has been rapidly developed. The ultimate goal of these hard copies is to bring the image quality closer to that of a silver halide photograph. In particular, the color reproducibility, color density, texture, resolution, glossiness, light resistance, etc. should be closer to that of a silver halide photograph. It is a development goal.

  As such hard copy recording methods, various recording methods such as sublimation type thermal transfer method, ink jet method, electrostatic recording method, etc. are proposed in addition to direct photographing of a display displaying an image with a silver salt photograph. Has been put to practical use. Among these recording methods, printers based on the ink jet method have the advantages of being easy to make full color and having less printing noise, and thus are rapidly spreading in recent years.

  The ink jet recording method is capable of recording high-definition images with a relatively simple apparatus, and has been rapidly developed in various fields. In addition, there are various uses, and a recording medium or ink suitable for each purpose is used.

  The recording medium used in the ink jet recording method is such that the ink-receiving layer is a support itself such as paper such as plain paper, or an ink absorption layer on a support that also serves as an absorber such as coated paper. Or an ink-absorbing layer coated on a non-absorbing support such as a resin-coated paper or a polyester film. Among these, the recording medium of the type in which an ink absorbing layer is coated on a non-absorbing support has a high glossiness, glossiness, depth, etc. due to its high surface smoothness and low waviness. It is preferably used for an output that requires a high quality texture such as a salt photograph. Furthermore, as a glossy recording medium having high gloss and gloss, a swelling type recording medium in which a water-soluble binder such as polyvinyl pyrrolidone or polyvinyl alcohol is coated as an ink absorbing layer on a non-absorbent support, As the ink absorbing layer, a so-called void type recording medium is used in which a fine void structure is formed with inorganic fine particles and a binder, and the ink is absorbed into the void.

  On the other hand, an ink jet using an ink liquid using a pigment as a coloring material has been proposed aiming at a highly durable image. This is an ink using a dispersion liquid in which a pigment is dispersed as a coloring material, and the durability of an image using the same has been greatly improved as compared with that using a dye. However, in the ink using the pigment, the pigment does not soak into the recording medium and deposits on the surface. As a result, the gloss of the image portion made of the pigment is different from that of the white background on which the ink is not placed. A major problem with image quality such as rough surface at a high concentration part and a problem with storage stability with poor scratching properties such as scratches when rubbed have emerged.

  In order to solve this problem, an ink jet recording medium having a rough surface and diffusing reflected light to make the difference in gloss inconspicuous and reducing the contact area has been used for pigment ink. However, as a result of making the surface uneven, there was a drawback that only a rough image with low gloss could be obtained.

  As an attempt to improve the uniform gloss, there is a method of functionally separating the pigment fixing layer and the solvent absorbing layer (see, for example, Patent Documents 1 and 2). Further, an inkjet recording medium having a high 60 ° gloss is disclosed by disposing spherical particles having a refractive index of 1.65 or more on the surface (for example, see Patent Document 3). There is an attempt to increase image color and coating strength by putting titanium oxide and colloidal silica in the protective layer in a two-layer structure of a protective layer and an ink receiving layer (see, for example, Patent Document 4). However, even in these methods, there is a difference in gloss in the image obtained using the pigment ink, particularly a difference in gloss between the white background and the image portion, so that a non-uniform gloss is given and a uniform gloss image is obtained. It did not come.

  The present inventors have found that uniform glossiness can be achieved by forming the surface layer with inorganic fine particles having a specific high refractive index and a binder. In particular, it has been found that an ink jet recording medium excellent in ink absorbability can be obtained by providing a void type ink absorbing layer comprising a porous layer as a lower layer of the surface layer.

  However, if the ink absorption amount of the porous layer is not sufficiently large, the pigment aggregates when the ink overflows on the surface, and the printed portion has a metallic luster (so-called bronzing). As a result, the white background and the image portion The problem that the gloss difference becomes particularly large was revealed. Increasing the film thickness of the porous layer can increase the amount of ink absorbed by the porous layer. However, if the film thickness is increased, the porous layer may crack depending on the coating and drying conditions. When a crack with a size of several μm is formed on the porous layer, the inorganic fine particles in the surface layer coating solution are buried in the crack of the porous layer when the surface layer is dried when a surface layer is formed on it. As a result, the effect of eliminating the gloss difference cannot be realized.

  In addition to the problem of cracking, there is also a problem of cost increase due to an increase in raw materials. Although it is possible to prevent cracking by reducing the coating / drying speed of the porous layer to some extent, it is not sufficient, and the effect of lowering productivity due to a decrease in the coating speed is great.

In order to improve productivity, it is effective to layer the surface layer and the porous layer simultaneously. However, if the porous layer is thick, the drying shrinkage of the porous layer increases and the thin film shrinks by drying. A difference in shrinkage stress is generated between the surface layer having a small force and a problem such as peeling at the interface occurs.
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 circumstances, and the object of the present invention is to obtain a uniform gloss feeling over a white background and an image portion when printed with pigment ink, and has high scratch resistance, An object of the present invention is to provide an ink jet recording medium and an ink jet recording method for pigment ink that can obtain an image that is hardly noticeable even if scratched.

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

(Claim 1)
On the support, a surface layer containing inorganic fine particles having an average refractive index of 2.1 to 2.9 and a binder, gas phase method silica having an isolated silanol group ratio of 5.0 to 7.0, and polyvinyl alcohol are contained. An ink jet recording medium having a porous layer that has a porous volume ratio of 60% or more.

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

(Claim 3)
The inkjet recording medium according to claim 1 or 2, wherein the inorganic fine particles of the surface layer contain at least one selected from titanium oxide, cerium oxide, and zirconium oxide.

(Claim 4)
The ink jet recording medium according to claim 1, wherein the surface layer contains a cationic polymer.

(Claim 5)
The inkjet recording medium according to any one of claims 1 to 4, wherein the support is a non-absorbent support.

(Claim 6)
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.

  According to the present invention, when printed with pigment ink, a uniform glossy feeling is obtained across the white background and the image area, and the scratch resistance is high. A recording medium and an ink jet recording method can be provided.

  As a result of intensive studies, the present inventor has obtained 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 an isolated silanol group ratio of 5.0 to 7.0. An inkjet recording medium having a porous layer containing vapor-phase process silica and polyvinyl alcohol, wherein the porous layer has a void volume ratio of 60% or more, and is uniform over a white background and an image portion. It has been found that an ink jet recording medium can be obtained in which glossiness is obtained, scratch resistance is high, and an image that is not noticeable even if it is scratched is obtained.

  By arranging inorganic fine particles having a high refractive index in a specific range on the surface of the ink jet recording medium, the gloss of the white background is increased, and the difference in gloss from the printed portion is eliminated. Further, it was found that the scratch resistance is improved by the fine particles. Although details of this reason have not been elucidated, since inorganic fine particles with a high refractive index tend to have high crystallinity, when the image is rubbed, the inorganic fine particles with a high refractive index bite into the lower layer and generate a so-called anchor effect. I think that.

  In addition, by setting the void volume ratio of the porous layer of the inkjet recording medium having the above configuration to 60% or more, a sufficient ink absorption amount can be secured without increasing the film thickness of the porous layer. In addition, it is possible to prevent the ink from overflowing on the surface and agglomeration of the pigment to cause a so-called bronzing metal gloss, and as a result, the difference in gloss between the white background and the printed portion can be further reduced.

  In addition, by reducing the thickness of the porous layer, it is possible to reduce costs by reducing raw materials and improve productivity by increasing coating speed.

  Further, since the drying shrinkage force of the porous layer can be reduced by reducing the thickness of the porous layer, even if the porous layer and the surface layer are applied simultaneously, the difference in drying shrinkage stress between the two does not increase. There is no occurrence of peeling.

  Furthermore, since cracks do not occur in the porous layer, even if the surface layer is applied after forming the porous layer, the inorganic fine particles on the surface layer are not buried in the cracks, and the effect of eliminating the gloss difference of the present invention can be achieved. Can fully demonstrate.

  In the present invention, by using gas phase method silica having an isolated silanol group ratio of 5.0 to 7.0 as inorganic fine particles in the porous layer, the interparticle interaction is strengthened, and as a result, the skeleton that forms voids is formed. A high void volume ratio can be achieved by increasing the interaction and taking a strong three-dimensional network structure and drying while maintaining the gel state.

  The present invention will be described in detail below.

[Surface layer]
(Inorganic fine particles)
The inorganic fine particles (also referred to as inorganic filler) used for the surface layer are inorganic fine particles having an average refractive index of 2.1 to 2.9.

  In the present invention, the average refractive index means the refractive index when the inorganic fine particles are composed of one kind. In the case of a plurality of types, the refractive index is averaged by the mass fraction of each inorganic fine particle, and can be calculated by the mass fraction from the refractive index of each individual inorganic fine particle and the composition ratio of the inorganic fine particles. 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. 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. If the average refractive index is in the range of 2.1 to 2.9, the individual inorganic fine particles may be 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), zinc oxide (2.02), and tin oxide (2.093) can be used in combination.

  The product of the 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, uniform gloss can be obtained on the white background and the image, but if it is 1.7 μm or less, the gloss value at 60 degrees is increased, and further gloss can be obtained. The surface roughness in the present invention can be measured using RST / PLUS manufactured by WYKO. The surface roughness is preferably as small as possible from the viewpoint of preventing light scattering. Although light scattering is affected by the surface roughness and the refractive index of the surface layer, in the present invention, it is preferable to make the surface roughness particularly small because fine particles having a high refractive index are used for the surface layer as described above. It is preferable that the product has a constant value of 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 size is within this range, there is no particular limitation, but the range of 5 to 80 nm is particularly preferable. When the average primary particle size is less than 5 nm, the gap through which the surface ink passes becomes small, so that ink absorption deteriorates and ink leakage occurs. Will occur. This is because when the thickness is larger than 80 nm, the surface roughness increases, and the gloss deteriorates.

(binder)
A conventionally known hydrophilic resin is used as the binder for the surface layer. 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 does not desorb the inorganic particles in the surface layer, but it is used in the range of 1 to 200% by mass with respect to the inorganic fine particles. Preferably, it is 5 to 50%. If the amount of the binder is too much, the ink absorptivity is deteriorated.

  Various additives can be added to the coating solution for forming the surface 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. Organic solvents, high-boiling organic solvents, latex emulsions, anti-fading agents, UV absorbers, polyvalent metal compounds (water-soluble or water-insoluble), matting agents, silicone oils, etc. This is preferable in order to improve the water resistance and fixability later.

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 and the like. 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 dry film thickness of the surface layer is preferably 0.01 to 0.3 μm or 1.2 to 20 μm from the viewpoint of preventing light interference fringes. If it is less than 0.01 μm, the effect of gloss difference is not sufficiently exhibited, and if it exceeds 20 μm, the surface layer is cracked and the gloss is lowered.

(Porous layer)
Next, the porous layer (also referred to as an ink absorbing layer) will be described.

  The ink jet recording medium of the present invention has one or more porous layers, so-called ink absorbing layers. In general, the ink absorbing layer is roughly divided into a swelling type and a void type.

  As the swelling type, a water-soluble binder is used, for example, gelatin, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide or the like is applied alone or in combination, and this is used as an ink absorbing layer. As the void type, a mixture of fine particles and a water-soluble binder is applied and particularly glossy is preferable. As the fine particles, alumina or silica is preferable, and those using silica having a particle size of 0.1 μm or less are particularly preferable. As the water-soluble binder, gelatin, polyvinyl alcohol, polyvinyl pyrrolidone, polyethylene oxide or the like is preferably used alone or in combination. Of the above two types, in order to adapt to continuous high-speed printing, it is suitable that the ink absorption speed of the recording medium is faster. From this point, the void type can be particularly preferably used in the present invention.

  The porous layer is mainly formed by soft aggregation of a hydrophilic binder and inorganic fine particles. Conventionally, various methods for forming voids in a film are known. For example, a uniform coating solution containing two or more kinds of polymers is coated on a support, and these polymers are phase-separated from each other in the drying process. A method of forming voids by applying a coating liquid containing solid fine particles and a hydrophilic or hydrophobic resin on a support, and after drying, the inkjet recording medium is immersed in water or a liquid containing an appropriate organic solvent. , A method of creating voids by dissolving solid fine particles, a method of forming voids in a film by applying a coating liquid containing a compound having a property of foaming during film formation, and then foaming this compound in the drying process, porous A coating liquid containing porous solid fine particles and a hydrophilic binder on a support to form voids in or between the porous fine particles, a volume approximately equal to or larger than the hydrophilic binder Solid particles and or a coating solution containing a particulate oil and a hydrophilic binder is coated on a support, and a method of forming an air gap between the solid particles are known having. In the present invention, it is particularly preferable that the porous layer is formed by containing various inorganic solid fine particles having an average particle diameter of 400 nm or less.

(Gas-phase method silica having an isolated silanol group ratio of 5.0 to 7.0)
In the present invention, by using gas phase method silica having an isolated silanol group ratio of 5.0 to 7.0 as inorganic fine particles, a void volume ratio of 60% or more can be achieved even under high temperature drying conditions of 40 ° C. or higher. A more preferable range is 5.5 to 7.0. The higher the isolated silanol group ratio, the higher the interparticle interaction and the easier to obtain high voids. However, when the isolated silanol group ratio exceeds 7.0, the viscosity at the time of preparing the coating solution is high, which is not preferable for handling. Vapor phase silica is a silica typified by a process for hydrolyzing silicon tetrachloride in an oxygen / hydrogen burner at a high temperature of 1000 ° C. or higher. For example, Aerosil manufactured by Nippon Aerosil Co., Ltd. is commercially available. The isolated silanol group ratio can be adjusted by changing the water content of the vapor phase silica described later.

  In the present invention, in order to control the isolated silanol group ratio of the vapor-phase process silica, it is preferable to adjust the vapor-phase process silica by spraying water vapor.

  As a method of spraying water vapor, there are a method of spraying water vapor continuously while conveying vapor phase method silica, and a method of spraying water vapor while aeration of vapor phase method silica in a sealed batch.

  It is also preferable to adjust the water content of the vapor phase silica by storing the vapor phase silica at a humidity of 20 to 60% for 3 days or more.

  The isolated silanol group ratio referred to in the present invention is determined using FT-IR.

The vapor phase silica is dried at 120 ° C. for 24 hours, and the dried vapor phase silica is subjected to FT-IR measurement. Absorbance 3750Cm ^-1 attributable to Si-OH, determine the absorbance of 1870cm ^-1 attributable to Si-O-Si, a value obtained by the following formula was isolated silanol group ratio.

Isolated silanol group ratio (hereinafter, also referred to as IR ratio) = (Absorbance / 1870Cm absorbance ^-1 3750Cm ^-1)
In the present invention, the vapor phase silica preferably has an average particle size of 100 nm or less. Further, if it is 50 nm or less, a high print density can be obtained and the density fluctuation with time does not easily occur. The average particle diameter of the vapor-phase process silica is obtained as a simple average value (number average) by observing the cross section and surface of the porous layer with an electron microscope and determining the particle diameter of 100 arbitrary particles. Here, each particle size is represented by a diameter assuming a circle equal to the projected area.

  Other inorganic fine particles may be added to the porous layer. Examples of such inorganic fine particles 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, White inorganic pigments such as 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. Can be mentioned. The average particle size of the inorganic fine particles is determined by the same method as that of the vapor phase silica.

(Polyvinyl alcohol)
Polyvinyl alcohol used as a hydrophilic binder for the porous layer includes, in addition to ordinary polyvinyl alcohol obtained by hydrolyzing polyvinyl acetate, cation-modified polyvinyl alcohol and anion-modified polyvinyl alcohol having an anionic group. Such modified polyvinyl alcohols are also included.

  The polyvinyl alcohol obtained by hydrolyzing vinyl acetate preferably has an average degree of polymerization of 1,000 or more, and particularly preferably has an average degree of polymerization of 1,500 to 5,000. The saponification degree is preferably 70 to 100%, particularly preferably 80 to 99.5%.

  Examples of the cation-modified polyvinyl alcohol have primary to tertiary amino groups and quaternary ammonium groups in the main chain or side chain of the polyvinyl alcohol as described in JP-A-61-110483. Polyvinyl alcohol, which is 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-acrylamido-2,2-dimethylethyl) ammonium chloride and trimethyl- (3-acrylamido-3,3-dimethylpropyl) ammonium chloride. N-vinylimidazole, N-vinyl-2-methylimidazole, N- (3-dimethylaminopropyl) methacrylamide, hydroxylethyltrimethylammonium chloride, trimethyl- (2-methacrylamidopropyl) ammonium chloride, N- (1, 1-dimethyl-3-dimethylaminopropyl) acrylamide 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.

  Anion-modified polyvinyl alcohol is, for example, polyvinyl alcohol having an anionic group as described in JP-A-1-206088, as described in JP-A-61-237681 and JP-A-63-330779, Examples thereof include a copolymer of vinyl alcohol and a vinyl compound having a water-soluble group, and modified polyvinyl alcohol having a water-soluble group as described in JP-A-7-285265.

  Nonionic modified polyvinyl alcohol is, for example, a polyvinyl alcohol derivative obtained by adding a polyalkylene oxide group to a part of vinyl alcohol as described in JP-A-7-9758, and described in JP-A-8-25595. And a block copolymer of a vinyl compound having a hydrophobic group and vinyl alcohol. Polyvinyl alcohol can be used in combination of two or more, such as the degree of polymerization and the type of modification.

  Other hydrophilic binders may be used in combination with the porous layer of the present invention. Examples of such hydrophilic binders include gelatin, polyethylene oxide, polyvinyl pyrrolidone, polyacrylic acid, polyacrylamide, polyurethane, dextran, dextrin, color genin (κ, ι, λ, etc.), agar, pullulan, water-soluble polyvinyl butyral. , Hydroxyethyl cellulose, carboxymethyl cellulose and the like. Two or more of these water-soluble binders can be used in combination.

  The ratio of the inorganic fine particles to the total amount of the hydrophilic binder in the porous layer is preferably 3 to 15 times in terms of mass ratio. If the mass ratio is 3 times or more, the void volume ratio of the porous layer is good, it is easy to obtain a sufficient void volume, and an excessive hydrophilic binder can be prevented from swelling and closing the void during ink jet recording. On the other hand, when this ratio is 15 times or less, it is preferable that cracks hardly occur when the porous layer is applied as a thick film. The ratio of the fine particles to the particularly preferred hydrophilic binder is 3 to 7 times from the viewpoint of breakage of the dried coating film.

The amount of inorganic fine particles used in the ink absorption layer depends largely on the required ink absorption capacity, the porosity of the porous layer, the type of inorganic pigment, and the type of water-soluble binder, but generally 1 m ^{2 of} recording paper. Usually, it is 5-30 g, preferably 10-25 g.

(Void volume fraction)
The void volume ratio is the ratio of the void volume to the solid content volume in the porous layer having ink retention ability, and can be measured by a mercury intrusion method using, for example, a mercury porosimeter (such as Autopore IV9500 manufactured by Micromeritex Corporation). it can. In the present invention, the void volume ratio needs to be 60% or more. The upper limit of the void volume ratio is not particularly limited, but is approximately 75% or less in terms of obtaining a good film free from cracks due to coating and drying or bending.

  In the porous layer of the present invention, a cationic polymer can be used as a dispersion aid for inorganic fine particles. As the cationic polymer, the same polymer as the surface layer can be used.

  Various additives other than those described above can be used in the ink absorption layer of the ink jet recording medium of the present invention and other layers provided as necessary. For example, organic latex fine particles such as polystyrene, polyacrylic acid esters, polymethacrylic acid esters, polyacrylamides, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, or a copolymer thereof, urea resin, or melamine resin , Anionic, cationic, nonionic and amphoteric surfactants, UV absorbers described in JP-A-57-74193, JP-A-57-87988, and JP-A-62-261476, JP-A-57-74192, No. 57-87989, 60-72785, 61-146591, JP-A-1-95091, JP-A-3-13376, etc., JP-A-59-42993, 59- Nos. 52689, 62-280069, 61-242871 and JP-A-4-21 Optical brighteners described in No. 266, etc., pH adjusters such as sulfuric acid, phosphoric acid, citric acid, sodium hydroxide, potassium hydroxide, potassium carbonate, antifoaming agents, preservatives, thickeners, antistatic agents Various known additives such as an agent and a matting agent can also be contained.

  The ink absorbing layer may be composed of two or more layers. In this case, the structures of the ink absorbing layers may be the same or different from each other.

[Support]
As the support that can be used in the present invention, those conventionally known for inkjet recording media can be used as appropriate, and may be a water-absorbing support, but is preferably a non-water-absorbing support.

  In the case of an absorptive support, the support is distorted due to water absorption, so-called cockling occurs, and not only the quality is degraded, but also the gloss difference between the white background and the image area, which is the object of the present invention, is not sufficient. . This is because the apparent glossiness changes due to cockling.

  Examples of the water-absorbing support that can be used in the present invention include sheets and plates having general paper, cloth, wood, and the like. In particular, paper is excellent in water absorption of the substrate itself and It is most preferable because of its excellent cost. As the paper support, the main raw materials are chemical pulps such as LBKP and NBKP, mechanical pulps such as GP, CGP, RMP, TMP, CTMP, CMP, and PGW, and wood pulp such as waste paper pulp such as DIP. It is. In addition, various fibrous materials such as synthetic pulp, synthetic fiber, and inorganic fiber can be appropriately used as raw materials as necessary. If necessary, various conventionally known additives such as sizing agents, pigments, paper strength enhancers, fixing agents, fluorescent whitening agents, wet paper strength agents, cationizing agents and the like are added to the paper support. be able to. The paper support can be produced by mixing various fibrous materials such as wood pulp and various additives and using various paper machines such as a long net paper machine, a circular net paper machine, and a twin wire paper machine. Further, if necessary, the paper can be subjected to size press treatment with starch, polyvinyl alcohol or the like, various coating treatments, or calendar treatment on a paper making stage or a paper machine.

  Non-water-absorbing supports that can be preferably used in the present invention include transparent supports and opaque supports. Examples of the transparent support include films having materials such as polyester resins, diacetate resins, triatesate resins, acrylic resins, polycarbonate resins, polyvinyl chloride resins, polyimide resins, cellophane, and celluloid. Among them, those having a property of resisting radiant heat when used for overhead projectors (OHP) are preferable, and polyethylene terephthalate is particularly preferable. The thickness of such a transparent support is preferably 50 to 200 μm. Further, as the opaque support, for example, resin-coated paper (so-called RC paper) having a polyolefin resin coating layer in which white pigment or the like is added to at least one of the base paper, white pigment such as barium sulfate is added to polyethylene terephthalate. A so-called white pet is preferable. For the purpose of increasing the adhesive strength between the various supports and the ink absorbing layer, the support is preferably subjected to corona discharge treatment, subbing treatment or the like prior to application of the ink absorbing layer. Furthermore, the inkjet recording medium of the present invention is not necessarily colorless, and may be a colored recording sheet.

  In the ink jet recording medium 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 making using synthetic pulp such as polypropylene or synthetic fibers 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 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 the mass% of the 24 mesh residue defined by JIS-P-8207 and the 42 mesh residue. The sum of the mass% of the minutes is preferably 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 / m ² (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. 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) and / or high-density polyethylene (HDPE), but some other LLDPE, polypropylene, etc. can also be used. In particular, the polyethylene layer on the ink absorbing 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 titanium oxide content is usually 3 to 20% by mass, preferably 4 to 13% by mass, based on polyethylene. Polyethylene-coated paper can be used as glossy paper, or when the polyethylene is melt-extruded onto 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 water content in the paper is particularly preferably maintained at 3 to 10% by mass.

The method of applying various ink absorbing layers provided as necessary, such as the porous layer and the undercoat layer of the recording paper of the present invention, on the support can be appropriately selected from known methods. A preferred method is obtained by coating a coating liquid constituting each layer on a support and drying. In this case, two or more layers can be applied simultaneously. As the coating method, for example, a roll coating method, a rod bar coating method, an air knife coating method, a spray coating method, a curtain coating method, or an extrusion coating method using a hopper described in US Pat. No. 2,681,294 is preferable. Used.
The method for applying the surface layer defined above of the recording paper of the present invention can be appropriately selected from known methods.

〔ink〕
In the ink jet recording method of the present invention, an image is formed by discharging ink containing at least water, a water-soluble solvent and a color material onto the ink jet recording medium of the present invention.

  In the present invention, it is particularly preferable to use a pigment ink as a colorant 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 inkjet recording 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 composition 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.

  The printer that can be used in the present invention is not particularly limited as long as it has a recording paper storage unit, a transport unit, an ink cartridge, and an inkjet print head, such as a commercially available printer.

  The inkjet head to be used may be an on-demand system or a continuous system. In addition, as a discharge method, an electro-mechanical conversion method (for example, a single cavity type, a double cavity type, a bender type, a piston type, a shear mode type, a shared wall type, etc.), an electro-thermal conversion method (for example, a thermal type) Specific examples include an ink jet type, a bubble jet (R) type, and the like, an electrostatic suction type (for example, an electric field control type, a slit jet type, etc.), a discharge type (for example, a spark jet type, etc.), and the like. However, any discharge method may be used.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these. Unless otherwise specified, “%” in the examples represents “mass%”.

Example [Production of Inkjet Recording Medium]
(Production of vapor phase silica S-1 to S-3)
Gas phase method silica having a specific surface area of 300 m ² / g is put in a closed container, and the amount of water vapor sprayed and the time are changed so that the IR ratio of gas phase method silica as shown in Table 1 is changed. Was maintained at 1.96 Pa or less, and vapor-phase process silica S-1 to S-3 were produced. Table 1 shows the IR ratio of S-1 to S-3. The IR ratio of the vapor phase silica was determined by the method described in the detailed description.

(Preparation of vapor phase silica aqueous dispersion 1)
Using a jet stream inductor mixer manufactured by Mitamura Riken Kogyo Co., Ltd., 10 kg of the vapor phase silica S-1 was sucked and dispersed at room temperature in a solution obtained by adding 435 ml of ethanol to 35 l of pure water. Gas phase method silica aqueous dispersion 1 was prepared by finishing with pure water so that the content was 23%. The vapor phase silica aqueous dispersion contained 1% ethanol and had a pH of 2.8.

(Preparation of vapor phase silica aqueous dispersion 2)
Gas phase method silica water dispersion 2 was prepared in the same manner as gas phase method silica water dispersion 1 except that gas phase method silica S-1 was changed to gas phase method silica S-2.

(Preparation of vapor phase silica aqueous dispersion 3)
Gas phase method silica water dispersion 3 was prepared in the same manner as gas phase method silica water dispersion 1 except that gas phase method silica S-1 was changed to gas phase method silica S-3.

(Preparation of fine particle dispersion 1)
To 435 g of the vapor phase silica aqueous dispersion 1, 100 g of a 10% cationic polymer P-1 (containing 10% n-propanol and 2% ethanol) aqueous solution, 3.6 g boric acid, 0. 8 g was added with stirring at 3000 rpm at room temperature.

Subsequently, it was dispersed with a high-pressure homogenizer manufactured by Sanwa Kogyo Co., Ltd. at a pressure of 3000 N / cm ² , and the entire amount was finished with pure water so that the silica content was 18%, whereby a fine particle dispersion 1 was prepared. The obtained dispersion was filtered using a TCP-10 type filter manufactured by Advantex Toyo.

(Preparation of fine particle dispersion 2)
A fine particle dispersion 2 was prepared in the same manner as the fine particle dispersion 1, except that the vapor phase silica dispersion 1 was changed to the vapor phase silica dispersion 2.

(Preparation of fine particle dispersion 3)
A fine particle dispersion 3 was prepared in the same manner as the fine particle dispersion 1, except that the vapor phase silica dispersion 1 was changed to the vapor phase silica dispersion 3.

(Preparation of coating solution 1)
The following additives were sequentially mixed with 555 g of the fine particle dispersion 1 while stirring at 40 ° C., and finally the total amount was adjusted to 1000 g with pure water to prepare a coating solution 1.

8% aqueous solution of polyvinyl alcohol having a degree of polymerization of 3500 (PVA235 manufactured by Kuraray Co., Ltd.)
160g
8% aqueous solution of polyvinyl alcohol having a degree of polymerization of 4500 (PVA245 manufactured by Kuraray Co., Ltd.)
48g
(Preparation of coating solution 2)
A coating liquid 2 was prepared in the same manner as the coating liquid 1 except that the fine particle dispersion 1 was changed to the fine particle dispersion 2.

(Preparation of coating solution 3)
A coating liquid 3 was prepared in the same manner as the coating liquid 1 except that the fine particle dispersion 1 was changed to the fine particle dispersion 3.

(Preparation of porous layer 1)
The coating solution 1 is a polyethylene-coated paper in which both sides of a base paper having a thickness of 170 g / m ² are coated with polyethylene (containing 8% anatase-type titanium oxide in polyethylene on the ink absorption layer side, 0.05 g on the ink absorption layer side). / M ² gelatin undercoat layer, and a latex polymer having a Tg of about 80 ° C. on the opposite side as a back layer of 0.2 g / m ² ) using a bar coater so that the dry film thickness is 40 μm. After the application, it was dried with warm air to produce a porous layer 1.

(Preparation of porous layer 2)
A porous layer 2 was produced in the same manner as the porous layer 1 except that the coating solution 1 was changed to the coating solution 2.

(Preparation of porous layer 3)
A porous layer 3 was produced in the same manner as the porous layer 1 except that the coating solution 1 was changed to the coating solution 3.

(Preparation of inkjet recording medium 1)
An ink jet recording medium 1 was obtained by storing in a constant temperature bath at 40 ° C. and 80% RH without applying a surface layer to the porous layer 1.

(Preparation of surface layer coating solution 1)
While stirring to 333 g of titanium oxide aqueous dispersion (Ishihara Sangyo Co., Ltd., TSK-5), 250 g of polyvinyl alcohol (Kuraray Co., PVA224) 8% aqueous solution with a polymerization degree of 2400 was added, and the total amount was adjusted to 1000 g with pure water. Thus, a surface layer coating solution 1 was prepared.

(Preparation of surface layer coating solution 2)
250 g of titanium oxide aqueous dispersion (ISKhara Sangyo TSK-5) and 125 g of colloidal silica (Nissan Chemical Co., Snowtex OS) were mixed, and after stirring, polyvinyl alcohol having a polymerization degree of 2400 (Kuraray, PVA224) A surface layer coating solution 2 was prepared by adding 250 g of an 8% aqueous solution and adjusting the total amount to 1000 g with pure water.

(Preparation of surface layer coating solution 3)
A surface layer coating solution 3 was prepared by adding 250 g of an 8% aqueous solution of polyvinyl alcohol (Kuraray Co., PVA224) having a polymerization degree of 2400 to 1000 g of colloidal silica (Nissan Chemical Co., Snowtex OS) while stirring.

(Preparation of titanium oxide dispersion)
120 g of an aqueous 10% cationic polymer P-1 dispersant solution (containing 10% n-propanol and 2% ethanol) and 400 g of a titanium oxide aqueous dispersion (TSK-5, manufactured by Ishihara Sangyo Co., Ltd.) at room temperature The mixture was added with stirring at 3000 rpm, and then the pH was adjusted to 4.1 with a 1 mol / L-NaOH aqueous solution. Subsequently, it was dispersed with a high pressure homogenizer manufactured by Sanwa Kogyo Co., Ltd. at a pressure of 3000 N / cm ² , and the whole amount was finished with pure water so that the titanium oxide content was 20%. Prepared.

(Preparation of surface layer coating solution 4)
While stirring to 500 g of the above titanium oxide dispersion S-3, 250 g of an 8% aqueous solution of polyvinyl alcohol having a polymerization degree of 2400 (manufactured by Kuraray Co., Ltd., PVA224) was added, and the total amount was adjusted to 1000 g with pure water to prepare a surface layer coating solution. 4 was prepared.

(Preparation of inkjet recording medium 2)
On the porous layer 1, the surface layer coating solution 1 is applied with a wire bar while controlling the film thickness so that the dry film thickness becomes 2 μm, dried with warm air, and then a constant temperature bath at 40 ° C. and 80% RH. The ink-jet recording medium 2 was produced by storing for 12 hours.

(Preparation of inkjet recording medium 3)
An ink jet recording medium 3 was produced in the same manner as the ink jet recording medium 2 except that the pH of the surface layer coating solution 1 was changed to the Ra in Table 2 on the porous layer 1.

(Preparation of inkjet recording medium 4)
An ink jet recording medium 4 was produced in the same manner as the ink jet recording medium 2 except that the surface layer coating liquid 1 was changed to the surface layer coating liquid 2.

(Preparation of inkjet recording medium 5)
An ink jet recording medium 5 was produced in the same manner as the ink jet recording medium 2 except that the surface layer coating liquid 1 was changed to the surface layer coating liquid 3.

(Preparation of inkjet recording medium 6)
An ink jet recording medium 6 was produced in the same manner as the ink jet recording medium 2 except that the surface layer coating liquid 1 was changed to the surface layer coating liquid 4.

(Preparation of inkjet recording medium 7)
An ink jet recording medium 7 was produced in the same manner as the ink jet recording medium 2 except that the porous layer 1 was changed to the porous layer 2.

(Preparation of inkjet recording medium 8)
An ink jet recording medium 8 was produced in the same manner as the ink jet recording medium 2 except that the porous layer 1 was changed to the porous layer 2 and the dry film thickness was changed to 50 μm.

(Preparation of inkjet recording medium 9)
An ink jet recording medium 9 was produced in the same manner as the ink jet recording medium 2 except that the porous layer 1 was changed to the porous layer 3.

[Preparation of ink]
The pigment particles were dispersed so that the average particle size of the pigment particles was 0.2 to 0.3 μm with the following composition to prepare pigment dispersions of respective colors.

(Black pigment dispersion 1)
C. I Pigment Black-7 20 parts Polymer dispersant 5 parts Stearyl acrylate 75 parts (Yellow pigment dispersion 1)
C. I Pigment Yellow-12 10 parts Polymer dispersant 5 parts Stearyl acrylate 85 parts (Magenta pigment dispersion 1)
C. I Pigment Red-57: 1 15 parts Polymer dispersant 5 parts Stearyl acrylate 80 parts (Cyan pigment dispersion 1)
C. I Pigment Red-15: 3 20 parts Polymer dispersant 5 parts Stearyl acrylate 75 parts (White pigment dispersion 1)
Titanium oxide (anatase type: particle size 0.2 μm) 20 parts Polymer dispersant 5 parts Stearyl acrylate 85 parts An ink having the following composition was prepared using the above dispersion.

(Black ink 1)
Black pigment dispersion 1 15 parts Stearyl acrylate 65 parts Bifunctional aromatic urethane acrylate (molecular weight 1500) 10 parts Hexafunctional aliphatic urethane acrylate (molecular weight 1000) 5 parts Photopolymerization initiator (manufactured by Ciba Specialty Chemicals, Irgacure 184) 5 copies (yellow ink 1)
Yellow pigment dispersion 1 20 parts Stearyl acrylate 60 parts Bifunctional aromatic urethane acrylate (molecular weight 1500) 10 parts Hexafunctional aliphatic urethane acrylate (molecular weight 1000) 5 parts Photopolymerization initiator (manufactured by Ciba Specialty Chemicals, Irgacure 184) 5 copies (Magenta ink 1)
Magenta pigment dispersion 1 20 parts Stearyl acrylate 60 parts Bifunctional aromatic urethane acrylate (molecular weight 1500) 10 parts Hexafunctional aliphatic urethane acrylate (molecular weight 1000) 5 parts Photopolymerization initiator (manufactured by Ciba Specialty Chemicals, Irgacure 184) 5 copies (Cyan ink 1)
Cyan pigment dispersion 1 15 parts Stearyl acrylate 65 parts Bifunctional aromatic urethane acrylate (molecular weight 1500) 10 parts Hexafunctional aliphatic urethane acrylate (molecular weight 1000) 5 parts Photopolymerization initiator (manufactured by Ciba Specialty Chemicals, Irgacure 184) 5 copies (white ink 1)
White pigment dispersion 1 15 parts Stearyl acrylate 65 parts Bifunctional aromatic urethane acrylate (molecular weight 1500) 10 parts Hexafunctional aliphatic urethane acrylate (molecular weight 1000) 5 parts Photopolymerization initiator (manufactured by Ciba Specialty Chemicals, Irgacure 184) 5 parts [Measurement and evaluation of inkjet recording media]
The obtained inkjet recording medium was subjected to the following measurements and evaluations. The results are shown in Table 2.

(Ra)
The surface roughness Ra of the surface layer of the inkjet recording medium was measured using RST / PLUS manufactured by WYKO.

(Void volume fraction)
The void volume ratio of the porous layer of the inkjet recording medium was measured by a mercury intrusion method using a mercury porosimeter (manufactured by Micromeritex Corporation, Autopore IV9500).

(Image printing)
The ink liquid is mounted on an ink jet printer MC-2000 (manufactured by Seiko Epson Corporation), and cyan solid images and high-definition color digital standard image data “Bride” issued by the Japanese Standards Association are recorded on the ink jet recording media 1 to 8. Printed. This image was dried in an environment of 23 ° C. and 55% RH for 1 hour. Each inkjet recording medium was printed using what was stored at 23 ° C. for one day.

(Glossy uniformity)
Visual evaluation was performed by 15 people to determine whether there was a difference in gloss between the white background in the dress of the high-definition color digital standard image data “Bride” and the image of the other dress, and the following three-level evaluation was performed.

◎: Number of people who felt that there was a difference in gloss 0 to 1 ○: Number of people who felt that there was a difference in gloss 3-5 people △: Number of people who felt that there was a difference in gloss 6: 10 people ×: 11-15 people who feel that there is a difference in gloss (Scratch resistance)
The image was rubbed 5 times with Kimwipe S-200 (manufactured by Crecia), visually evaluated for the degree of surface scratches and the color fading of the image, and the following four grades were evaluated.

◎: Scratches and color fading are not observed ○: Scratches are scarce and no color fading is observed △: Scratches are slight and color fading is observed ×: Scratches are observed and color fading is also greatly recognized (crack resistance) )
The number of film surface cracks at 30 cm × 10 cm of each recording paper was measured visually.

  The results obtained as described above are shown in Table 2.

  From Table 2, it can be seen that the inkjet recording medium of the present invention is superior in gloss uniformity, scratch resistance, and crack resistance compared to the comparative inkjet recording medium.

Claims (6)

On the support, a surface layer containing inorganic fine particles having an average refractive index of 2.1 to 2.9 and a binder, gas phase method silica having an isolated silanol group ratio of 5.0 to 7.0, and polyvinyl alcohol are contained. An ink jet recording medium having a porous layer that has a porous volume ratio of 60% or more. 2. The ink jet recording medium according to claim 1, wherein a product of the surface roughness Ra (μm) of the surface layer and the average refractive index is 1.7 μm or less. The inkjet recording medium according to claim 1 or 2, wherein the inorganic fine particles of the surface layer contain at least one selected from titanium oxide, cerium oxide, and zirconium oxide. The ink jet recording medium according to claim 1, wherein the surface layer contains a cationic polymer. The inkjet recording medium according to any one of claims 1 to 4, wherein the support is a non-absorbent support. 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.