JP2015147368A - recording medium and image recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recording medium that has excellent ink absorption and uniform and high glossiness, suppresses generation of a bronze tone, and has surface properties similar to a baryta paper with appropriate roughness.SOLUTION: The recording medium comprises a substrate, and an ink-receiving layer and a gloss layer on the substrate. The ink-receiving layer shows 60-degree specular glossiness of 20% or more specified by JIS Z8741. The gloss layer contains organic fine particles having an average particle diameter of 10 nm or more and 100 nm or less and first inorganic fine particles having an average particle diameter of 60 nm or less, and satisfies the following conditions (1) and (2). (1) A mass ratio of the organic fine particles to the first inorganic fine particles is 5/95 or more and 30/70 or less; and (2) an arithmetic average surface roughness of the gloss layer is 0.5 μm or more and 0.8 μm or less.

Description

  The present invention relates to a recording medium and an image recording method.

  2. Description of the Related Art In recent years, an ink jet recording method in which fine droplets of ink are ejected by various operating principles and adhered to a recording medium such as paper to record images, characters, and the like is frequently used. This type of recording apparatus has features such as high speed and low noise, easy multi-coloring, large recording pattern flexibility, and no development and fixing. For this reason, it is rapidly spreading in various applications including information equipment as various image recording apparatuses. Furthermore, an image formed by the multicolor ink jet recording method can obtain a recording that is comparable to multicolor printing by a plate making method or printing by a color photographic method. For this reason, when the number of produced copies is small, it is cheaper than ordinary multicolor printing and printing, and is widely applied to the field of full-color image recording.

  Under such circumstances, further high speed and high image quality in the ink jet recording method are widely demanded, and a recording medium as a final output product has been studied. In general, the recording medium has an ink-absorbing and porous ink-receiving layer in which silica particles or alumina hydrate particles, which are pigment particles, are held with a binder.

  On the other hand, as the surface quality of the recording medium that affects the image quality, baryta paper having high gloss and appropriate roughness is used as a photograph in addition to the glossy surface and the matte surface. Therefore, a recording medium is also required to have a baryta-like surface quality in addition to gloss. In order to obtain such a recording medium, it is necessary to have a glossy layer, to be excellent in printability of dye ink, and to eliminate uneven glossiness that occurs when pigment ink is printed. The recording medium had a tendency to be poor in absorbability.

  In response to the above problems, Patent Document 1 discloses a recording medium having an ink receiving layer containing inorganic fine particles having an average secondary particle diameter of 500 nm or less and a resin binder on a support, and a surface layer on the ink receiving layer. ing. The surface layer of this recording medium is formed by using organic fine particles having a particle size of 15 nm or more and 400 nm or less, or inorganic fine particles having an average primary particle size of 50 nm or less in combination. Further, the surface layer contains 40% by volume or more of organic fine particles, and the arithmetic average roughness is 0.3 μm or more and 3.5 μm or less. In the recording medium of Patent Document 1, it is possible to eliminate a sense of incongruity due to a difference in glossiness between a printing portion and a blank paper portion that occurs when pigment ink is printed by the above configuration.

JP 2008-126550 A

The present inventors have examined the prior art and found that there are the following problems.
The inventors of the present invention examined the surface properties of silver salt baryta paper in detail. As a result, the silver salt baryta paper has an arithmetic average roughness Ra of 0.5 μm or more and 0.8 μm or less when measured with a reference length of 2.5 mm as defined in JIS-B-0601 and a cutoff value of 0.8 mm. It was in range. Moreover, it turned out that 60 degree specular glossiness prescribed | regulated by JIS-Z-8741 is 60% or more and 80% or less.

  In the method of Patent Document 1, although high gloss is achieved with various surface properties, the surface of the silver salt baryta paper having a 60 ° specular gloss of 60% or more in a range where the surface roughness Ra exceeds 0.5 μm. No one has achieved sex. In the present situation, an inkjet recording medium having such a rough surface has not achieved a high glossiness.

  In addition, the conventional method is sufficient for the development of bariter-like surface, improvement in ink absorbency and gloss difference between the printed part and the white paper part when pigment ink is applied, and the point that the ink has a term color developing property. Had not been considered.

  The present invention has been made in view of the above situation. The object of the present invention is to have a high glossiness, excellent ink absorbability, improve the gloss difference between the printed portion and the white paper portion when a pigment ink is applied, and have a high color development property while maintaining a barita-like surface. It is an object of the present invention to provide a recording medium having a property (a texture comparable to silver salt baryta paper).

One embodiment is:
A substrate;
On the substrate, at least one ink receiving layer having a 60-degree specular gloss specified in JIS Z8741 of 20% or more, and
A gloss layer containing organic fine particles having an average particle diameter of 10 nm or more and 100 nm or less and first inorganic fine particles having an average particle diameter of 60 nm or less on the ink receiving layer, wherein the following conditions (1) and (2) are satisfied: With a gloss layer to fill,
The present invention relates to a recording medium.
(1) The mass ratio of the organic fine particles to the first inorganic fine particles is 5/95 or more and 30/70 or less.
(2) The arithmetic average roughness of the surface of the glossy layer is 0.5 μm or more and 0.8 μm or less.

  High glossiness, excellent ink absorption, improved gloss difference between printed area and white paper area when applied with pigment ink, high color development and balita-like surface (comparable to silver salt baryta paper) A recording medium having a texture that can be provided.

A recording medium according to an embodiment of the present invention includes a base material, at least one ink receiving layer on the base material, and a gloss layer on the ink receiving layer. The ink receiving layer has a 60 ° specular glossiness of 20% or more as defined in JIS Z8741. The gloss layer contains organic fine particles having an average particle diameter of 10 nm or more and 100 nm or less, and first inorganic fine particles having an average particle diameter of 60 nm or less. The gloss layer satisfies the following conditions (1) and (2).
(1) The mass ratio of the organic fine particles to the first inorganic fine particles is 5/95 or more and 30/70 or less.
(2) The arithmetic average roughness of the surface of the gloss layer is 0.5 μm or more and 0.8 μm or less.

  The glossy layer of the recording medium of the present embodiment contains organic fine particles having an average particle diameter of 10 nm or more and 100 nm or less and first inorganic fine particles having an average particle diameter of 60 nm or less. Thereby, the gloss layer can have a uniform and dense porous structure. Accordingly, the surface of the recording medium not printed with ink (the surface of the glossy layer) can have a high glossiness. Further, it can have high permeability (hereinafter referred to as “ink absorbability”) of the ink component (in the case of dye ink, the ink itself, in the case of pigment ink, water or a high-boiling organic solvent in which the pigment is dispersed). .

  By setting (organic fine particles) / (first inorganic fine particles), which is the mass ratio of the organic fine particles and the first inorganic fine particles in the gloss layer, to 5/95 or more and 30/70 or less, high gloss and high ink Absorbability can be made compatible. That is, when the mass ratio is less than 5/95, that is, when the organic fine particles are small, the recording medium cannot obtain a high glossiness. Further, when the mass ratio is larger than 30/70, that is, when there are too many organic fine particles, it is difficult to ensure ink absorbency even if high glossiness is obtained.

  The ink receiving layer of the recording medium of the present embodiment has a 60 ° specular gloss of 20% or more. By setting the 60 ° specular glossiness of the ink receiving layer to 20% or more, the glossiness of the recording medium viewed from the glossy layer side can be further improved and uniform glossiness can be obtained.

  Further, by setting the arithmetic average roughness of the gloss layer surface to 0.5 μm or more and 0.8 μm or less, the recording medium can have a variator-like surface property with an appropriate roughness. That is, when the arithmetic average roughness exceeds 0.8 μm, the sharpness of the formed image may be impaired. On the other hand, when the arithmetic average roughness is less than 0.5 μm, the surface of the gloss layer becomes a “glossy surface”, and reflection of external light may occur.

  As described above, the recording medium of the present embodiment has a uniform and high glossiness equal to or higher than that of the printing unit even before ink is applied. Accordingly, even when a pigment ink is applied to the recording medium and printing is performed, even if a coating made of a pigment having a high glossiness is formed on the printing portion on the glossy layer, the difference in glossiness between the non-printing portion and the printing portion is reduced. be able to. As a result, the generation of bronze can be suppressed. In addition, since the gloss layer has a porous structure, when pigment ink is printed on the recording medium, main components other than the pigment penetrate the gloss layer and penetrate into the ink receiving layer. Therefore, the recording medium of the present embodiment can have excellent ink absorbability.

  Since the dye constituting the dye ink exists as a single molecule, when the dye ink is printed on the recording medium, the entire ink component permeates through the porous glossy layer and penetrates into the ink receiving layer. Therefore, the recording medium of the present embodiment can have excellent ink absorbability. Further, the dye ink does not form a film on the surface of the recording medium like the pigment ink, and bronzing due to the difference in gloss between the printed portion and the unprinted portion does not occur.

  As described above, the gloss improvement by the gloss layer of the present embodiment is manifested in the entire print density region of the ink, and a uniform gloss image with excellent color developability can be obtained. In addition, since this recording medium can have a variator-like surface with an appropriate roughness, it is possible to achieve both a writer-like surface and high glossiness. Furthermore, the recording medium of the present embodiment can have excellent ink absorbability.

  The recording medium of the present embodiment only needs to have an ink receiving layer on at least one surface of the substrate and a gloss layer on the ink receiving layer. That is, the ink receiving layer and the gloss layer may be provided in this order on one surface of the substrate, or the ink receiving layer and the gloss layer may be provided in this order on both surfaces of the substrate facing each other. Further, the ink receiving layer may be one layer or more, and may be one layer or two layers or more.

  As described above, since the arithmetic average roughness of the surface of the glossy layer is 0.5 μm or more and 0.8 μm or less, the recording medium of the present embodiment has an ink receiving layer and is referred to as “barrier surface”. It corresponds to a recording medium having a surface other than “”. The “arithmetic average roughness of the glossy layer surface” is measured on the surface of the recording medium having the glossy layer at a reference length of 4.0 mm and a cut-off value of 0.8 mm as defined in JIS B0601: 2001.

  The 60 degree specular gloss of the ink receiving layer can be 20% or more by various methods. For example, if the coating amount after drying of the ink receiving layer is increased, the 60 degree specular gloss can be increased. Further, the 60-degree specular gloss can be controlled by changing the constituent material of the ink receiving layer or changing the method of forming the ink receiving layer.

  The arithmetic average roughness of the surface of the glossy layer can be 0.5 μm or more and 0.8 μm or less by various methods. For example, when the surface of the substrate is subjected to an uneven surface treatment using an uneven surface roll or the like, the surface shape of the glossy layer formed thereon also reflects the surface shape of the substrate. For this reason, the arithmetic mean roughness of the surface of a glossy layer is controllable by controlling the surface shape of a base material. Even when a substrate having the same surface shape is used, if the thickness of the ink receiving layer or gloss layer formed thereon is increased, the surface of the gloss layer tends to be smooth. For this reason, the arithmetic average roughness of the surface of the glossy layer can also be controlled by the thickness of the ink receiving layer or the glossy layer. Furthermore, the arithmetic average roughness of the surface of the glossy layer can be controlled by subjecting the glossy layer itself to uneven processing or changing the constituent material of the glossy layer.

  Below, each layer which comprises the recording medium of this embodiment is demonstrated in detail.

1. Recording Medium An image can be recorded on the recording medium of the present embodiment by applying both pigment ink and dye ink. However, as described above, in the related recording medium, when pigment ink is applied, the gloss difference between the printed portion and the unprinted portion is large, and bronzing tends to occur. In contrast, the recording medium of the present embodiment can suppress the occurrence of bronzing by reducing the difference in glossiness between the printed portion and the unprinted portion even when the pigment ink is applied in this way. Therefore, the recording medium of the present embodiment is preferably a recording medium for applying a pigment ink.
(1) Substrate Conventionally known materials used for recording media can be appropriately used as the substrate, and either a water-absorbing substrate or a non-water-absorbing substrate can be used. As the substrate, paper such as cast-coated paper, baryta paper, and resin-coated paper (resin-coated paper coated on both sides with a resin such as polyolefin) can be preferably used. In addition, transparent thermoplastic films such as polyethylene, polypropylene, polyester, polylactic acid, polystyrene, polyacetate, polyvinyl chloride, cellulose acetate, polyethylene terephthalate, polymethyl methacrylate, and polycarbonate can be preferably used.

  In addition, a sheet material (synthetic paper or the like) made of an appropriately sized paper, a non-size paper, a coated paper, a film made opaque by filling with an inorganic substance or fine foaming can be used. A sheet made of glass or metal may be used. Furthermore, in order to improve the adhesive strength between these substrates and the ink receiving layer, the surface of the substrate can be subjected to corona discharge treatment or various undercoat treatments. Among the above-mentioned base materials, it is preferable to use a gas-permeable base material such as paper subjected to appropriate sizing. Further, the surface of the base material may be subjected to a concavo-convex treatment so as to have a predetermined surface shape.

  In the paper substrate, 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 as necessary. Can be added.

(2) Ink-receiving layer The ink-receiving layer can contain various additives in addition to the second inorganic fine particles, the binder, the crosslinking agent, and the pH adjuster. These components are described in detail below.

(A) Second inorganic fine particles As the second inorganic fine particles used in the ink receiving layer, light calcium carbonate, magnesium carbonate, kaolin, barium sulfate, aluminum silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, wet and White pigment fine particles such as dry silica sol and alumina hydrate are preferred. In addition, the second inorganic fine particles may be used alone or in combination. Of these, silica particles and alumina hydrate particles are preferably used, and alumina hydrate particles are more preferably used from the viewpoint of ink absorbability and the like.

(B) Binder The ink receiving layer contains a binder. The binder is not particularly limited as long as it is a material capable of binding the second inorganic fine particles such as the above-mentioned alumina hydrate and forming a film and does not impair the effects of the present invention. Can be used.

  From the viewpoint of ink absorbability, the content of the binder in the ink receiving layer is preferably 50 parts by mass or less and more preferably 30 parts by mass or less with respect to 100 parts by mass of the second inorganic fine particles. Further, from the viewpoint of the binding property of the ink receiving layer, the ratio is preferably 5.0 parts by mass or more, and more preferably 8.0 parts by mass or more.

  As binder, polyvinyl alcohol (PVA), oxidized starch, etherified starch, phosphate esterified starch, carboxymethylcellulose, hydroxyethylcellulose, casein, gelatin, soybean protein, polyvinylpyrrolidone, maleic anhydride resin, styrene-butadiene copolymer , Conjugated polymer latex such as methyl methacrylate-butadiene copolymer, acrylic polymer latex such as polymer of acrylic ester and methacrylic ester, vinyl polymer latex such as ethylene-vinyl acetate copolymer, melamine resin , Urea resin, polymer or copolymer resin of acrylic acid ester or methacrylic acid ester such as polymethyl methacrylate, polyurethane resin, unsaturated polyester resin, vinyl chloride-vinyl acetate copolymer, polyvinyl chloride Butyral, alkyd resins and the like are used.

  The said binder can be used individually or in mixture of multiple types. Among them, the most preferably used binder is PVA. As this PVA, normal PVA obtained by hydrolyzing polyvinyl acetate can be mentioned. This PVA is more preferably one having an average degree of polymerization of 1500 or more and 5000 or less. The saponification degree is preferably 70 or more and 100 or less.

  In addition to this, modified PVA such as PVA whose end is cation-modified or anion-modified PVA having an anionic group can be used.

(C) Crosslinking agent The crosslinking agent is not particularly limited as long as it does not impair the effects of the present invention. When PVA is used as a binder, a crosslinking agent that can be cured by causing a crosslinking reaction with PVA is preferable. As the crosslinking agent, boric acid is particularly preferable. In this case, examples of boric acid that can be used include not only orthoboric acid (H ₃ BO ₃ ) but also metaboric acid and hypoboric acid. It is preferable to use orthoboric acid.

  The amount of boric acid used is preferably in the range of 0.2 equivalents or more and 1.2 equivalents or less with respect to PVA in the ink receiving layer. In addition, about said "equivalent", the amount of crosslinking agents which reacts completely with the amount of hydroxyl groups which PVA has theoretically shall be 1.0 equivalent. By setting it as the above range, the temporal stability of the ink receiving layer coating liquid can be particularly improved. In general, when an ink receiving layer is formed, the ink receiving layer coating solution is used for a long time. By setting the content of boric acid in the ink receiving layer coating liquid within the above range, it is excellent that the viscosity of each coating liquid rises during long-time use and the occurrence of gelled products occurs. Can be prevented. For this reason, it is not necessary to frequently change the coating liquid for the ink receiving layer and clean the coater head, and it is possible to easily prevent the productivity of the recording medium from being lowered. Further, if the content of boric acid in the ink receiving layer coating liquid is within the above range, it is excellently prevented that the ink receiving layer is likely to have point-like surface defects, and a uniform and good surface is obtained. be able to.

(D) pH adjuster In the ink receiving layer coating solution, for example, the following acids can be appropriately added as pH adjusters.
Formic acid, acetic acid, glycolic acid, oxalic acid, propionic acid, malonic acid, succinic acid, adipic acid, maleic acid, malic acid, tartaric acid, citric acid, benzoic acid, phthalic acid.
Isophthalic acid, terephthalic acid, glutaric acid, gluconic acid, lactic acid, aspartic acid, glutamic acid, pimelic acid, suberic acid, methanesulfonic acid.
Inorganic acids such as hydrochloric acid, nitric acid, phosphoric acid.

  For example, when alumina hydrate is used as the second inorganic fine particles, it is preferable to use a monobasic acid in order to disperse the alumina hydrate in water. For this reason, it is preferable to use organic acids, such as formic acid, acetic acid, glycolic acid, and methanesulfonic acid, hydrochloric acid, nitric acid, etc. among the said pH adjusters.

(E) Additives As additives for the ink receiving layer coating liquid, pigment dispersants, fastness improvers, and the like are used in such a range that the contact angle with respect to pure water on the surface of the ink receiving layer after forming the ink receiving layer does not change significantly. It can be used as appropriate.

(F) Coating method for ink-receiving layer coating liquid For example, the following coating method can be used for coating the ink-receiving layer coating liquid so that an appropriate coating amount can be obtained. Apply off-machine.
・ Various curtain coaters and coaters using the extrusion method.
・ Coater using slide hopper method.
In addition, at the time of coating, for the purpose of adjusting the viscosity of the coating liquid for the ink receiving layer, the coating liquid may be heated, or the coater head can be heated.

  Further, for drying the coating liquid after coating for the ink receiving layer, for example, a hot air dryer such as a straight tunnel dryer, an arch dryer, an air loop dryer, a sine curve air float dryer, or the like can be used. In addition, a dryer using infrared rays, a heated dryer, a microwave, or the like can be appropriately selected and used.

When producing a recording medium having one ink-receiving layer, the absolute dry coating amount of the ink-receiving layer coating liquid varies depending on the required ink absorption capacity, glossiness, composition of the receiving layer, etc., but 15 g / M ² or more and 50 g / m ² or less is preferable. If it is 15 g / m ² or more, it is possible to suppress a decrease in ink absorbency, and if it is 50 g / m ² or less, it is possible to suppress a decrease in crack strength. Further, from the viewpoint of glossiness, it is preferably 35 g / m ² or more.

(3) Glossy layer In related technologies, glossy layers are often disclosed as generally smooth surfaces. However, by using the gloss layer of the present embodiment, high glossiness can be achieved while having a non-smooth variator-like surface property. For example, the 60-degree specular gloss, which is an index of gloss, can be greatly increased.

  The increase in glossiness due to the provision of the glossy layer is affected by the thickness, refractive index and transparency of the glossy layer. If the thickness is the same, the higher the refractive index, the higher the reflectance. If it is a refractive index, the higher the transparency, the higher the reflectance. These relationships can be estimated approximately by calculation using the optical thickness multiplied by the refractive index and thickness of the glossy layer and the refractive index of the ink receiving layer and using the Fresnel coefficient described in the optical books. I can do it.

  The gloss layer contains organic fine particles having an average particle diameter of 10 nm or more and 100 nm or less, and first inorganic fine particles having an average particle diameter of 60 nm or less. The average particle size of the first inorganic fine particles is the primary particle size. When the average particle diameter exceeds 100 nm, the gloss on the surface of the gloss layer becomes low. For example, when pigment ink is printed on a recording medium, it is difficult to obtain a gloss equivalent to that of the print portion. On the other hand, when the average particle size is smaller than 10 nm, the ink absorbability of the glossy layer is inferior. The average particle size of the organic fine particles is preferably 10 nm or more and 30 nm or less. There is no particular lower limit on the average particle size of the first inorganic fine particles, but it is preferably 1 nm or more.

  The mass ratio between the organic fine particles and the first inorganic fine particles is 5/95 or more and 30/70 or less. Preferably, the mass ratio is 5/95 or more and 20/80 or less.

  Further, the arithmetic average roughness (Ra) of the surface of the gloss layer is 0.5 μm or more and 0.8 μm or less. The arithmetic average roughness is preferably 0.5 μm or more and 0.7 μm or less. When the thickness is in the range of 0.5 to 0.7 μm, the recording medium can have a surface property close to that of a silver salt photograph baryta paper, and can be suitably used.

  The components contained in the gloss layer coating liquid may include the organic fine particles and the first inorganic fine particles, and if necessary, a very small amount of binder, water or an organic solvent as a fine particle dispersion medium. In addition to these components, a component that does not remain locally by forming a film on the surface of the ink receiving layer and is absorbed with water or an organic solvent to the ink receiving layer side can be included. Specifically, these components can contain various surfactants, various inorganic salts (for example, zirconium acetate), various image preservatives, water-soluble fluorescent whitening agents, and the like.

  Below, the material which a glossy layer contains is demonstrated in detail.

(A) Organic fine particles Organic fine particles are, for example, polymer fine particles in a dispersed state in a medium. Examples of the material include acrylic polymer, styrene-acrylic copolymer, vinyl acetate-acrylic copolymer, ethylene. -Vinyl chloride copolymer, vinyl acetate polymer, ethylene-vinyl acetate copolymer, chlorinated polyolefin polymer, multi-component copolymer such as ethylene-vinyl acetate-acrylic, styrene butadiene copolymer, acrylonitrile butadiene copolymer , Methyl methacrylate butadiene copolymer, carboxylated styrene butadiene copolymer, carboxylated acrylonitrile butadiene copolymer, carboxylated methyl methacrylate butadiene copolymer, polyvinyl chloride, polyvinylidene chloride, polyester, polyolefin, polyurethane , Polymethacrylate, polytetrafluoroethylene, polymethacrylate, polycarbonate, polyvinyl acetal resin, rosin ester resin, episulfide resin, epoxy resin, silicone resin, silicone-acrylic resin, etc. I can do it.

  Further, those in which sulfur atoms are introduced into the monomers of these polymers for the purpose of increasing the refractive index, and those in which a fluorine substituent is introduced in order to improve the weather resistance or to lower the refractive index can be preferably used. For example, when polymer fine particles having a high refractive index are used, the coating amount of the glossy layer can be reduced when the same glossiness is required. The organic fine particles are preferably prepared and used as an aqueous emulsion, and may contain some organic solvent as a film forming aid. More preferably, an emulsion of polyurethane particles is used. One kind of organic fine particles may be used, or two or more kinds may be mixed and used.

(B) First inorganic fine particles The first inorganic fine particles are not only used as a material for forming a glossy layer in the same manner as the organic fine particles, but also, for example, control of the friction coefficient of the surface of the recording medium and control of ink absorption. Can be added.

  The first inorganic fine particles contained in the gloss layer have an average particle size of 60 nm or less. When the average particle diameter exceeds 60 nm, the glossiness of the gloss layer is lowered and the fixability of the first inorganic fine particles is also lowered.

  The first inorganic fine particles of the glossy layer include silica, alumina, rutile titanium dioxide, anatase titanium dioxide, zinc oxide, zinc sulfide, white lead, antimony oxides, zinc antimonate, lead titanate, potassium titanate, Zirconium oxide, cerium oxide, hafnium oxide, tantalum pentoxide, niobium pentoxide, yttrium oxide, chromium oxide, tin oxide, molybdenum oxide, ATO (antimony tin oxide), ITO (indium tin oxide), etc. They can be mixed and used, and these composite oxides or composite sulfides can also be used widely. Among the first inorganic fine particles, silica, alumina, zinc oxide, zirconium oxide, cerium oxide, antimony oxide, and titanium oxide are preferable in consideration of price and availability. As for the silica used for the gloss layer, colloidal silica is preferably used, and cationic colloidal silica particles having an average particle diameter of 60 nm or less are more preferable.

  Cationic colloidal silica particles can be prepared by making the surface of anionic colloidal silica particles cationic by various organic and inorganic surface treatments. Among them, it is preferable to use cationic colloidal silica particles surface-treated with alumina from the viewpoint of the stability of the dispersion and the availability. When the colloidal silica particles are cationic, when the glossy layer coating liquid containing the cationic colloidal silica particles is applied on the ink receiving layer, the aggregation of the coating liquid on the surface of the ink receiving layer is suppressed. And the color developability of the ink is improved. On the contrary, when the gloss layer coating liquid containing anionic colloidal silica particles is applied, the coating liquid aggregates on the surface of the ink receiving layer, and the color developability of the ink decreases.

  The cationic colloidal silica particles are more preferably monodispersed and spherical. “Monodispersibility” means that a plurality of particles are not associated in a dispersion (cationic colloidal silica). That is, the monodisperse cationic colloidal silica is one in which so-called cationic colloidal silica particles are not associated. When the associated cationic colloidal silica particles such as beaded are used, the glossiness of the gloss layer is lowered.

  The first inorganic fine particles to be used may be one kind or a mixture of two or more kinds. When two or more kinds of first inorganic fine particles are mixed and used, the first inorganic fine particles having the same surface charge sign may be mixed from the viewpoint of the temporal stability of the coating liquid for forming the gloss layer. preferable.

(C) Particle size The average particle size of the organic fine particles and the first inorganic fine particles is measured by a dynamic light scattering method. More specifically, “Structure of Polymers (2) Scattering Experiments and Morphological Observation Chapter 1 Light Scattering” (edited by Kyoritsu Publishing Polymer Society), or J. Chem. Phys., 70 (B), 15Apl., 3965 The average particle diameter can be determined from analysis using the cumulant method described in (1979). When the average particle diameter is measured by the dynamic light scattering method, if fine particles having different particle diameters are mixed, the decay of the time correlation function from the scattered light has a distribution. By analyzing this time correlation function using the cumulant method, the average (<Γ>) and variance (μ) of the decay rate can be obtained. Since the decay rate (Γ) is expressed as a function of the particle diffusion coefficient and the scattering vector, the hydrodynamic average particle diameter can be obtained using the Stokes-Einstein equation. The average particle size of the organic fine particles and the first inorganic fine particles can be easily measured using, for example, a zeta potential / particle size measurement system ELS Z-2 (manufactured by Otsuka Electronics Co., Ltd.).

(D) Gloss layer coating solution The gloss layer coating solution contains organic fine particles having an average particle size of 10 nm or more and 100 nm or less and first inorganic fine particles having an average particle size of 60 nm or less. In the solid content in the gloss layer coating liquid, the mass ratio of the organic fine particles to the first inorganic fine particles is 5/95 or more and 30/70 or less. In the present embodiment, the gloss layer can be formed by coating the above-described gloss layer coating liquid on the ink receiving layer.

  In addition to the organic fine particles and the first inorganic fine particles, the gloss layer coating solution includes a thickener, an antifoaming agent, a dot adjusting agent, a preservative, a pH adjusting agent, an antistatic agent, a conductive agent, and the like. Various additives may be added.

  The solid content concentration of the gloss layer coating liquid is preferably in the range of 0.05% by mass to 5% by mass, more preferably in the range of 0.1% by mass to 3% by mass, and particularly 0.15% by mass. % Or more and 2% by mass or less is preferable.

(E) Coating Method for Gloss Layer Coating Solution Various coating methods used for coating the ink receiving layer coating solution can be used as the coating method for the gloss layer coating solution. Further, the gloss layer coating liquid is applied at the same time as the ink receiving layer is formed, at the same time when the previously formed ink receiving layer is semi-cured or after the formed ink receiving layer is cured. Is possible. In order to avoid mixing the ink receiving layer and the gloss layer, it is preferable to apply the gloss layer coating liquid after the ink receiving layer is cured. The absolutely dry coating amount of the gloss layer coating solution is preferably 0.1 g / m ² or more and less than 0.5 g / m ² , and preferably 0.2 g / m ² or more and less than 0.4 g / m ^2. It is more preferable. If the coating amount is 0.1 g / m ² or more, the scratch resistance is particularly good, and if it is less than 0.5 g / m ² , the ink absorbability is particularly good.

  The method for curing the formed glossy layer is not particularly limited, and a known drying method that can be used for curing the ink receiving layer can be suitably used.

  Hereinafter, materials used for the recording medium of the present embodiment will be described in detail.

2. Image Recording Method An image can be recorded on the recording medium of this embodiment by applying either pigment ink or dye ink, but it is preferable to apply pigment ink. The method for applying ink to the recording medium is not particularly limited, but it is preferable to use an ink jet recording method. This method is a method of recording an image on a recording medium by ejecting ink with an ink jet recording head. Examples of the method for ejecting ink include a method for applying mechanical energy to the ink and a method for applying thermal energy to the ink. In the present embodiment, it is particularly preferable to employ an ink jet recording method using thermal energy. Except for using the recording medium of the present embodiment, the steps of the ink jet recording method can be known.

  Hereinafter, the present invention will be described more specifically with reference to examples. The following examples are specific examples shown for a deeper understanding of the present invention, and the present invention is not limited to these specific examples as long as the gist thereof is not exceeded. Also, “part” and “%” in the text are based on mass unless otherwise specified.

<Preparation of base material>
(Production of resin-coated substrate)
Add 20 parts of light calcium carbonate into a slurry of 100 parts of hardwood bleached kraft pulp, add 2 parts of cationic starch, 0.3 part of an alkenyl succinic anhydride neutral sizing agent, mix well, and did. This papermaking raw material is dried using a long-mesh multi-cylinder paper machine until the water content becomes 10%, and a 7% solution of oxidized starch is applied 4 g / m ² on both sides with a size press, dried, and the water content is 7%. To a base paper having a basis weight of 110 g / m ² . A resin composition comprising 70 parts of low density polyethylene and 20 parts of low density polyethylene was melt-extruded and applied to both the front and back surfaces of the base paper to a coating amount of 30 g / m ² . Immediately after this, using a cooling roll having irregularities of various irregular shapes on the surface, five types of molding processes were performed on the polyethylene surface while cooling. The difference in the molding was performed by adjusting the density and the height of the unevenness, thereby changing the arithmetic average roughness Ra of each substrate. As described above, base materials A to E having a basis weight of 270 g / m ² were prepared. Arithmetic average roughness Ra of each substrate is 0.60 (μm) for A, 0.40 (μm) for B, 0.80 (μm) for C, 0.3 (μm) for D, and 0.00 for E. 9 (μm).

(Preparation of air permeable substrate)
In the production of the polyethylene resin-coated paper A, the base paper of the polyethylene resin-coated paper was used as it was without being coated with the polyethylene resin composition. The arithmetic average roughness (Ra) value of the surface of the gas permeable substrate 1 on which the ink receiving layer is formed was 0.6 μm.

<Preparation of coating solution for ink receiving layer>
In pure water, alumina hydrate: Dispersal HP14 (trade name, manufactured by Sasol, second inorganic fine particles) was added as inorganic alumina hydrate so that the solid content concentration was 30%. Next, methanesulfonic acid was added to 100 parts of this alumina hydrate so as to be 1.5 parts and stirred to obtain a colloidal sol. The obtained colloidal sol was appropriately diluted with pure water so that the solid content concentration of the alumina hydrate was 25% to obtain colloidal sol 1.

  On the other hand, polyvinyl alcohol (PVA235, manufactured by Kuraray Co., Ltd., polymerization degree: 3500, saponification degree: 88%) was dissolved in ion-exchanged water to obtain a PVA aqueous solution having a solid content of 8.0%. Then, the PVA aqueous solution prepared in the colloidal sol prepared above is 8% in terms of PVA solid content ((binder) / (alumina hydrate) × 100) with respect to the solid content of alumina hydrate. Mixed. Next, a 5.0% boric acid aqueous solution was mixed with the solid content of alumina hydrate so as to be 1.5 parts in terms of boric acid solid content to obtain a coating solution for an ink receiving layer. .

<Preparation of gloss layer coating liquid>
Monodispersed, spherical cationic colloidal silica particles 20% aqueous dispersion slurry (trade name: Snowtex AK-L, manufactured by Nissan Chemical Industries) and 30% emulsion of cationic polyurethane particles (trade name: Superflex 620) Manufactured by Daiichi Kogyo Seiyaku Co., Ltd.). At this time, it mixed so that the cationic colloidal silica particle in a liquid mixture might be 90 parts, and the emulsion of a cationic polyurethane particle might be 10 parts (mass part of a cationic polyurethane particle). The resulting solution had a solid content concentration of 0.5%. Here, the cationic colloidal silica particles correspond to the first inorganic fine particles, and the cationic polyurethane particles correspond to the organic fine particles.

  When the average particle size was measured using a zeta potential / particle size measurement system ELS Z-2 (manufactured by Otsuka Electronics Co., Ltd.), the average particle size of the cationic colloidal silica particles was 45 nm. Moreover, the cationic polyurethane particle | grains were measured similarly and the average particle diameter was 30 nm.

  A surfactant (trade name: Neugen TDX50, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) is added to the obtained mixed liquid so that the solid content is 0.005% with respect to the total amount of the coating liquid. A liquid was obtained.

[Example 1]
On the base material A, an ink receiving layer coating solution was applied so that the coating amount after drying was 35 g / m ² and dried at 60 ° C. to provide an ink receiving layer. On the obtained ink receiving layer, a gloss layer coating solution is applied so that the coating amount after drying is 0.2 g / m ^2, and further dried at 60 ° C. to obtain a recording medium 1. It was.

[Example 2]
A recording medium 2 was produced in the same manner as in Example 1 except that the coating amount after drying of the ink-receiving layer coating liquid of Example 1 was changed to 20 g / m ² .

Example 3
A recording medium 3 was produced in the same manner as in Example 1 except that the base material A in Example 1 was changed to the base material B.

Example 4
A recording medium 4 was produced in the same manner as in Example 1 except that the base material A in Example 1 was changed to the base material C.

Example 5
A recording medium 5 was produced in the same manner as in Example 1 except that the substrate A in Example 1 was changed to the gas-permeable substrate 1.

Example 6
The cationic polyurethane particles in the gloss layer coating liquid were changed to cationic polyurethane particles (organic fine particles) having an average particle diameter of 10 nm. Specifically, Superflex 650 (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) was used instead of Superflex 620 (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.). Otherwise, the same operation as in Example 1 was performed to obtain the recording medium 6.

Example 7
The cationic polyurethane particles in the gloss layer coating solution were changed to cationic polyurethane particles (organic fine particles) having an average particle diameter of 70 nm. Specifically, Hydran CP-7060 (trade name, manufactured by DIC) was used instead of Superflex 620 (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.). Otherwise, the same operation as in Example 1 was performed to obtain the recording medium 7.

Example 8
The same operation as in Example 1 was carried out except that 94 parts of the cationic colloidal silica particles and 6 parts of the emulsion of the cationic polyurethane particles (the mass of the cationic polyurethane particles) were used in the gloss layer coating liquid. Recording medium 8 was obtained.

Example 9
The same operation as in Example 1 was performed except that 71 parts of the cationic colloidal silica particles and 29 parts of the emulsion of the cationic polyurethane particles (the mass of the cationic polyurethane particles) were used in the gloss layer coating liquid. A recording medium 9 was obtained.

Example 10
The coating amount after drying of the ink receiving layer coating liquid of Example 6 was changed to 20 g / m ² , 71 parts of cationic colloidal silica particles in the gloss layer coating liquid, The emulsion was 29 parts. Except for this, the recording medium 10 was produced in the same manner as in Example 6.

Example 11
The coating amount after drying of the ink receiving layer coating liquid of Example 7 was changed to 20 g / m ² . Further, 94 parts of the cationic colloidal silica particles and 6 parts of the emulsion with the cationic polyurethane particles (mass fraction of the cationic polyurethane particles) in the coating liquid for the gloss layer were used. Except for this, the recording medium 11 was produced in the same manner as in Example 7.

[Comparative Example 1]
A recording medium 12 was obtained in the same manner as in Example 1 except that the gloss layer coating solution was not applied.

[Comparative Example 2]
A recording medium 13 was produced in the same manner as in Example 1 except that the coating amount after drying of the ink-receiving layer coating liquid of Example 1 was changed to 18 g / m ² .

[Comparative Example 3]
A recording medium 14 was produced in the same manner as in Example 1 except that the base material A in Example 1 was changed to the base material D.

[Comparative Example 4]
A recording medium 15 was produced in the same manner as in Example 1 except that the base material A in Example 1 was changed to the base material E.

[Comparative Example 5]
The cationic polyurethane particles in the gloss layer coating solution were changed to cationic polyurethane particles having an average particle size of 220 nm. Specifically, Hydran CP-7040 (trade name, manufactured by DIC) was used instead of Superflex 620 (trade name, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.). Otherwise, the same operation as in Example 1 was performed to produce the recording medium 16.

[Comparative Example 6]
The cationic colloidal silica particles (average particle size 45 nm) in the coating solution for the glossy layer were changed to cationic colloidal silica particles having an average particle size of 70 nm. Specifically, cationic colloidal silica (trade name: Snow) Tex AK-YL (manufactured by Nissan Chemical Industries, Ltd.) was used instead of Snowtex AK-L (trade name, manufactured by Nissan Chemical Industries, Ltd.). Otherwise, the same operation as in Example 1 was performed to obtain the recording medium 17.

[Comparative Example 7]
The same operation as in Example 1 was performed except that 96 parts of the cationic colloidal silica particles and 4 parts of the emulsion of the cationic polyurethane particles (the mass of the cationic polyurethane particles) were used in the gloss layer coating liquid. A recording medium 18 was obtained.

[Comparative Example 8]
The same operation as in Example 1 was carried out except that 31 parts of the cationic colloidal silica particles and 69 parts of the emulsion of the cationic polyurethane particles (mass content of the cationic polyurethane particles) in the gloss layer coating liquid were used. A recording medium 19 was obtained.

<Evaluation of recording medium>
Next, the arithmetic average roughness (Ra) and 60 degree specular gloss of each recording medium obtained by the above method were measured as follows.

(Measurement method of arithmetic average roughness (Ra))
Measuring device: Kosaka Laboratory Surfcorder SE3500
Measurement conditions: Measured according to JIS B0601: 2001 with a cutoff value of 0.8 mm and an evaluation length of 4.0 mm.

(60 degree specular gloss)
The 60-degree specular gloss was measured with respect to the surface of the ink receiving layer before forming the glossy layer and the surface of the glossy layer after forming the recording medium. The 60-degree specular gloss was measured by the method described in JIS Z8741. As the apparatus, VG2000 (trade name) manufactured by Nippon Denshoku Industries Co., Ltd. was used.

  Moreover, the following evaluation was performed about each recording medium. The evaluation criteria are shown below.

[Balita feeling]
The balita feeling was evaluated according to the following criteria using the above arithmetic average roughness and 60 degree specular gloss.
A: The 60-degree specular gloss and arithmetic average roughness sufficiently satisfy the barita-like surface properties.
B: 60 degree specular gloss or arithmetic average roughness is slightly inferior, but satisfies the surface properties of the baryta.
C: 60 degree specular gloss and arithmetic average roughness are slightly inferior, but satisfy the surface properties of the baryta.
D: The 60-degree specular gloss or arithmetic average roughness is greatly inferior and does not satisfy the surface properties of the baryta.

[Ink absorbency]
The dye ink absorptivity of the recording surface (surface having an ink receiving layer and a glossy layer) of each recording medium was evaluated. Using a photo printer (trade name: PIXUS MG6130 manufactured by Canon Inc.) using an inkjet method, a 100% duty solid batch of black, cyan, magenta, and yellow as a recording medium in a photographic paper “silk-tone” mode Is printed. Since ink absorptivity and beading are substantially correlated, the ink absorptivity of the recording medium was evaluated by evaluating beading. Evaluation was performed visually and the rank was determined based on the following evaluation criteria.
A: No beading is observed.
B: Although beading is slightly observed, there is no practical problem.
C: The beading is clearly observed.

〔bronze〕
The bronze of the recording surface (surface having an ink receiving layer and a gloss layer) of each recording medium was evaluated. Using a photo printer (trade name: PIXUS Pro 9500 manufactured by Canon Inc.) using an inkjet method, monochrome printing was checked in a photographic paper “silk tone” mode. Then, 12 types of 1 square inch solid images having different RGB values were formed on the recording medium by changing RGB by 25 from (255, 255, 255) to (0, 0, 0). The portion where the metallic luster on the bronze with reddish color was generated at the place where the gradation of the monochrome image was switched was evaluated based on the following evaluation criteria.
A: Bronze is not observed.
B: Bronze is observed somewhat, but there is no practical problem.
C: Bronze is clearly observed.

  The above measurement results and evaluation results are shown in Table 1 below.

  From the results shown in Table 1, it can be seen that the recording medium of the present invention was almost “A” or “B” in terms of the bary feeling, absorbency, and bronze, and good results were obtained. The recording medium of the present invention has a high glossiness of 60% or more and 80 or less, and the arithmetic average roughness Ra of the glossy layer is 0.5 μm or more and 0.8 μm or less, and has a writer-like surface property. I understand.

Claims (8)

A substrate;
On the substrate, at least one ink receiving layer having a 60-degree specular gloss specified in JIS Z8741 of 20% or more, and
A gloss layer containing organic fine particles having an average particle diameter of 10 nm or more and 100 nm or less and first inorganic fine particles having an average particle diameter of 60 nm or less on the ink receiving layer, wherein the following conditions (1) and (2) are satisfied: With a gloss layer to fill,
A recording medium comprising:
(1) The mass ratio of the organic fine particles to the first inorganic fine particles is 5/95 or more and 30/70 or less.
(2) The arithmetic average roughness of the surface of the glossy layer is 0.5 μm or more and 0.8 μm or less.   2. The recording medium according to claim 1, wherein the arithmetic average roughness of the surface of the glossy layer is 0.5 μm or more and 0.7 μm or less.   The recording medium according to claim 1, wherein the organic fine particles are polyurethane particles.   The recording medium according to claim 1, wherein the first inorganic fine particles are colloidal silica particles.   The recording medium according to claim 1, wherein the ink receiving layer contains second inorganic fine particles and a binder.   The recording medium according to claim 5, wherein the second inorganic fine particles are alumina hydrate particles.   The recording medium according to claim 1, wherein the recording medium is a recording medium for applying pigment ink by an inkjet recording method.   An image recording method comprising applying a pigment ink to the recording medium according to any one of claims 1 to 7 by an ink jet recording method.