JP4141994B2 - Inkjet recording material - Google Patents

Description

  The present invention provides an ink jet recording material having both high white paper gloss, high ink absorption, and extremely low print portion haze.

  Inkjet recording has no noise and can be printed at high speed, and has been adopted rapidly for terminal printers in recent years. Also, by using a plurality of ink nozzles, it is easy to perform multicolor recording, and multicolor ink jet recording is performed by various ink jet recording methods. In particular, the use of an ink jet printer capable of forming a complex image quickly and accurately as a hard copy creation apparatus for image information such as characters, various figures and photographs created by a computer has attracted attention. Furthermore, with the rapid spread of digital cameras in recent years, digital photographic images have become familiar and inkjet printers equipped with a photographic-only mode and ink for outputting these images with an inexpensive inkjet printer are also rapidly spreading.

  In these photographic image applications, usually high gloss is required. As a means for enhancing gloss in an ink jet recording medium, it is known to apply colloidal silica on a porous ink receiving layer (see, for example, Patent Document 1, Patent Document 2, and Patent Document 3).

However, the colloidal silica described in the prior art as described above has a coefficient of variation greater than 0.15, and the ink jet recording materials according to these techniques have ink absorptivity, glossiness, and print portion haze. At the same time was not fully satisfied.
JP-A-6-183134 JP 2000-37944 A JP 2003-94800 A

  The problem to be solved by the present invention is to provide an ink jet recording material having high white paper gloss and extremely low print portion haze without causing a decrease in ink absorbency even when a colloidal silica layer is formed on the surface layer. is there.

  1. In an inkjet recording material having a porous ink receiving layer mainly composed of silica fine particles having an average secondary particle diameter of 500 nm or less on the support and a surface layer mainly composed of colloidal silica, the colloidal silica is 80 nm. An ink jet recording material comprising monodispersed colloidal silica having a coefficient of variation of 0.15 or less.

  It is possible to provide an ink jet recording material that is excellent in gloss of white paper, has sufficient ink absorptivity, and has extremely low haze in the printed portion.

  As a result of investigating why the absorption rate is hindered in an inkjet recording material using a porous ink receiving layer and a surface layer composed mainly of colloidal silica, the present inventors have found that colloidal silica formed on the surface is formed. It has been found that the packing state of the main layer greatly affects the absorption rate.

  Specifically, this packing state greatly depends on the coefficient of variation of the colloidal silica particles used. The coefficient of variation referred to here is obtained by dividing the standard deviation of the particle diameter of the colloidal silica particles by the average diameter. When the coefficient of variation exceeds 0.15, the colloidal silica particles forming the surface layer contain a relatively large amount of relatively small colloidal silica particles and relatively large colloidal silica particles. Silica particles have an adverse effect. For example, relatively small colloidal silica particles take a packing state that enters into the gaps between other colloidal silica particles, resulting in a decrease in the gaps between the particles, which may cause a decrease in absorption rate. understood. In addition, since the relatively large colloidal silica particles have high Rayleigh scattering intensity due to the particles, it has been found that when the printed surface is observed obliquely, the printed surface haze appears to be slightly clouded. .

  When colloidal silica having a monodispersity with a coefficient of variation of 0.15 or less is used for the surface layer, the colloidal silica particles are uniformly packed, so that the gaps between the particles are uniformly formed. It has been found that there is no reduction, and there are few relatively large colloidal silica particles, and no print portion haze is observed, leading to the present invention.

  In determining the monodispersibility in the present invention, an electron micrograph of the colloidal silica particles was taken, and the diameter of 500 or more colloidal silica particles was measured at random, and the average diameter and the standard deviation were determined. The coefficient of variation indicating the sex was calculated.

  There is a preferred range for the average particle size of the colloidal silica used for the surface layer. For example, when colloidal silica having an average particle diameter of 100 nm is used, the influence on the decrease in ink absorbency is slightly smaller than when colloidal silica having an average particle diameter of 50 nm is used. However, when the colloidal silica particles become large, the Rayleigh scattering intensity due to the particles becomes high, and when the colloidal silica particles exceed 80 nm, printing portion haze starts to occur. In the present invention, it is necessary to use colloidal silica having an average particle size of 80 nm or less, and it is more preferable to use colloidal silica having an average particle size of 60 nm or less. Since the ink absorbability starts to decrease when the particle size becomes small, the particle size is preferably 15 nm or more, and more preferably 25 nm or more. The most preferred average particle size is in the range of 25 nm to 50 nm.

  Colloidal silica is supplied as a colloidal solution in which ultrafine particles of silicic anhydride are dispersed in water or an organic solvent as a dispersion medium. The highly monodispersed colloidal silica used in the present invention can be produced by a so-called sol-gel method obtained by hydrolyzing and condensing alkoxysilane using ammonia or the like in an aqueous solvent. These can be obtained in various particle sizes, for example, as the Quartron series manufactured by Fuso Chemical Industry Co., Ltd.

  Also, colloidal silica of a type made cationic by alumina surface treatment can be preferably used as long as the average particle size and coefficient of variation are satisfied.

Drying solid content of the surface layer composed mainly of colloidal silica is preferably 0.8 g / m ² or less as colloidal silica, more preferably not more than ^{0.4g / m 2, 0.2g / m} 2 or less is particularly preferred. At least 0.02 g / m ² or more is required to improve glossiness by coating the surface layer. The content ratio of colloidal silica in the surface layer is 70% by mass or more, preferably 80% by mass or more, more preferably 90% by mass or more, and particularly preferably 98% by mass with respect to the total solid content of the surface layer. That's it.

  In the present invention, a known coating method can be used as a method for coating a surface layer mainly composed of colloidal silica. For example, the slide bead method, curtain method, extrusion method, air knife method, roll coating method, rod bar coating, etc., which are applied simultaneously with the coating liquid that forms a porous ink receiving layer mainly composed of silica fine particles. However, it is preferable to sequentially apply from the viewpoint of obtaining higher gloss. When performing sequential application, it may be performed continuously on the same line.

  In the case of sequential application, after a porous ink receiving layer mainly composed of silica fine particles is applied, a sufficient volume of voids is formed in the ink receiving layer in the middle of drying or at the end of drying. It is preferable to apply a surface layer containing colloidal silica as a main component at a given time.

Therefore, the time when the surface layer mainly composed of colloidal silica is applied is a stage in the middle of drying after the application liquid for the ink receiving layer is applied, or a stage after the drying is completed. In the present invention, the surface layer coating liquid containing colloidal silica as a main component is preferably applied at a coating amount of 90% by volume or less of the void volume of the ink receiving layer. The lower limit of the supply amount of the coating solution is that it is necessary to be able to form a surface layer mainly composed of colloidal silica sufficient for gloss improvement and to be stably applied. From the viewpoint of coating stability, 10 ml / m ² or more is desirable. . Here, the void volume of the ink receiving layer means the void volume at the time when the surface layer mainly composed of colloidal silica is applied. The void volume is preferably in the range of 15 to 50 ml / m ² from the viewpoint of ink absorption performance.

In the present invention, when the void volume of the ink receiving layer is less than 40 ml / m ² , the coating liquid supply amount of the surface layer mainly composed of colloidal silica is 90% by volume or less, more preferably 80% by volume or less. Is good. When the void volume is in the range of 40 to 50 ml / m ² , the coating solution supply amount of the surface layer mainly composed of colloidal silica is 80 volume% or less, more preferably 65 volume% or less of the void volume.

Among the void volumes of the ink receiving layer referred to in the present invention, the void volume after drying is measured and processed using a mercury porosimeter (Autopore II 9220; manufactured by micro meritics instrument corporation). By multiplying the cumulative pore volume (ml / g) from a radius of 3 nm to 400 nm by the coating solid content (g / m ² ) of the ink receiving layer, a numerical value per unit area (m ² ) can be obtained.

  In addition, the void volume in the case of applying a surface layer mainly composed of colloidal silica before reaching the drying end point of the ink receiving layer is the residual water content of the ink receiving layer immediately before the surface layer coating mainly composed of colloidal silica is infrared. Obtained by a moisture meter or the like, and obtained by subtracting the residual moisture content from the void volume after completion of the drying.

  From the viewpoint of uniformity of the surface layer mainly composed of colloidal silica, it is preferable that the surface layer coating liquid mainly composed of colloidal silica is absorbed instantaneously by the ink receiving layer in order to reduce the chance of disturbance. The coating viscosity measured at 35 ° C. is preferably 10 mPa · s or less.

  In carrying out the present invention by sequential coating, an extrusion method, a slide bead method, a coating device having a slit for uniformly flowing a coating solution in the width direction of coating, such as a slot die coater, and an oblique gravure roll It is preferable to use a coating apparatus to be used, and it is particularly preferable to use a slanted gravure roll having a roll diameter of 100 mm or less by reverse and kiss touch.

  In the practice of the present invention, the coating composition of the surface layer composed mainly of colloidal silica is sufficient for the original purpose of the present invention to adjust the concentration of colloidal silica alone, and other components are required. However, binders, additives, and surfactants can be added as appropriate for each application. The addition amount in the case of adding a binder is 10% by mass or less, preferably 5% by mass or less, more preferably 3% by mass or less, and particularly preferably 1% by mass or less with respect to colloidal silica. The addition of a component that greatly changes the surface shape, such as a matting agent, is not preferable because it impairs gloss.

  Next, a porous ink receiving layer mainly composed of silica fine particles having an average secondary particle diameter of 500 nm or less will be described. The main component means that at least 50% by mass, preferably 60% by mass or more, and particularly preferably 70% by mass or more of the total solid content of the ink receiving layer is composed of silica fine particles.

  Amorphous synthetic silica can be roughly classified into wet method silica, gas phase method silica, and others depending on the production method. Wet method silica is further classified into precipitation method silica, gel method silica, and sol method silica according to the production method. Precipitated silica is produced by reacting sodium silicate and sulfuric acid under alkaline conditions, and the silica particles that have grown are agglomerated and settled, and are then commercialized through the steps of filtration, washing, drying, pulverization and classification. Precipitated silica is commercially available, for example, from Nippon Silica Co., Ltd. as a nip seal, and from Tokuyama Co., Ltd. as Toku Seal. Gel silica is produced by reacting sodium silicate and sulfuric acid under acidic conditions. During aging, the microparticles dissolve and reprecipitate so as to bind the other primary particles, so that the distinct primary particles disappear and form relatively hard aggregated particles having an internal void structure. For example, it is commercially available from Nippon Silica as nip gel and from Grace Japan as syloid and silo jet. The sol method silica is also called colloidal silica, and is obtained by heating and aging a silica sol obtained through metathesis of sodium silicate acid or through an ion exchange resin layer. For example, it is commercially available as Snowtex from Nissan Chemical Industries, Ltd. Yes.

  Vapor phase silica is also called a dry method as opposed to a wet method, and is generally made by a flame hydrolysis method. Specifically, a method of making silicon tetrachloride by burning with hydrogen and oxygen is generally known, but silanes such as methyltrichlorosilane and trichlorosilane can be used alone or silicon tetrachloride instead of silicon tetrachloride. Can be used in a mixed state. Vapor phase silica is commercially available as Aerosil from Nippon Aerosil Co., Ltd. and QS type from Tokuyama Co., Ltd.

In the present invention, vapor phase silica is particularly preferably used. The average primary particle diameter of the vapor phase silica used in the present invention is preferably 30 nm or less, and preferably 15 nm or less in order to obtain higher gloss. More preferably, an average primary particle diameter of 3 to 15 nm (especially 3 to 10 nm) and a specific surface area by the BET method of 200 m ² / g or more (preferably 250 to 500 m ² / g) are used. The average primary particle diameter as used in the present invention is an average particle diameter obtained by observing the diameter of a circle equal to the projected area of each of 100 primary particles existing within a certain area by observation of fine particles with an electron microscope. The BET method referred to in the present invention is one of the powder surface area measurement methods by the vapor phase adsorption method, and is a method for obtaining the total surface area, that is, the specific surface area of a 1 g sample from the adsorption isotherm. is there. Usually, nitrogen gas is often used as the adsorbed gas, and the most frequently used method is to measure the amount of adsorption from the change in pressure or volume of the gas to be adsorbed. The most prominent expression for expressing the isotherm of multimolecular adsorption is the Brunauer, Emmett, and Teller formula, called the BET formula, which is widely used for determining the surface area. The adsorption amount is obtained based on the BET equation, and the surface area is obtained by multiplying the area occupied by one adsorbed molecule on the surface.

  Vapor phase silica is preferably dispersed in the presence of a cationic compound. The average secondary particle diameter of the dispersed vapor phase method silica is 500 nm or less, preferably 10 to 300 nm, and more preferably 20 to 200 nm. As a dispersion method, gas phase method silica and a dispersion medium are premixed by ordinary propeller stirring, turbine type stirring, homomixer type stirring, etc., and then a media mill such as a ball mill, a bead mill, a sand grinder, a high pressure homogenizer, an ultrahigh pressure, etc. It is preferable to perform dispersion using a pressure disperser such as a homogenizer, an ultrasonic disperser, a thin film swirl disperser, or the like. The average secondary particle diameter of the silica fine particles referred to in the present invention is determined by observing the ink receiving layer of the obtained recording material with an electron microscope.

  In the present invention, wet process silica pulverized to an average secondary particle diameter of 500 nm or less can also be preferably used. The wet process silica used in the present invention is preferably a wet process silica having an average primary particle diameter of 50 nm or less, preferably 3 to 40 nm, and an average aggregate particle diameter (particle diameter before pulverization) of 5 to 50 μm. . In the present invention, it is preferable to pulverize these wet process silicas in the presence of a cationic compound to an average secondary particle size of 500 nm or less, preferably about 20 to 200 nm.

  Since the wet process silica produced by a normal method has an average aggregate particle diameter of 1 μm or more, it is used after being finely pulverized. As a pulverization method, a wet dispersion method in which silica dispersed in an aqueous medium is mechanically pulverized can be preferably used. At this time, the increase in the initial viscosity of the dispersion is suppressed, high concentration dispersion is possible, and the pulverization / dispersion efficiency is increased so that the particles can be further pulverized. It is preferable to use precipitated silica of 5 μm or more. By using a high-concentration dispersion, the productivity of recording paper is also improved. The oil absorption is measured based on the description of JIS K-5101.

  As a specific method for obtaining wet method silica fine particles having an average secondary particle diameter of 500 nm or less of the present invention, first, silica particles and a cationic compound are mixed in water (whichever comes first or at the same time). And each dispersion or aqueous solution may be mixed, and at least one dispersion device such as a sawtooth blade type dispersion device, a propeller blade type dispersion device, or a rotor stator type dispersion device is used. To obtain a preliminary dispersion. If necessary, an appropriate low boiling point solvent may be added. The higher the solid content concentration of the silica pre-dispersion, the higher the concentration. However, since the dispersion becomes impossible when the concentration is too high, the preferred range is 15 to 40% by mass, and more preferably 20 to 35% by mass. Next, by applying a stronger mechanical means, a wet process silica fine particle dispersion having an average secondary particle diameter of 500 nm or less is obtained. As the mechanical means, a known method can be adopted, for example, a media mill such as a ball mill, a bead mill, a sand grinder, a high pressure homogenizer, a pressure disperser such as an ultra high pressure homogenizer, an ultrasonic disperser, and a thin film swirl disperser. Can be used.

  As the cationic compound used for the dispersion of the gas phase method silica and the wet method silica, a cationic polymer or a water-soluble metal compound can be used. As the cationic polymer, polyethyleneimine, polydiallylamine, polyallylamine, alkylamine polymer, JP-A-59-20696, JP-A-59-33176, JP-A-59-33177, JP-A-59-155088, Sho 60-11389, Sho 60-49990, Sho 60-83882, Sho 60-109894, Sho 62-198493, Sho 63-49478, Sho 63-115780, Shosho 63-280681, No. 1-40371, No. 6-234268, No. 7-125411, No. 10-193976, etc. The polymer having is preferably used. In particular, diallylamine derivatives are preferably used as the cationic polymer. In terms of dispersibility and dispersion viscosity, the molecular weight of these cationic polymers is preferably about 2,000 to 100,000, and particularly preferably about 2,000 to 30,000.

  Examples of the water-soluble metal compound include water-soluble polyvalent metal salts, and among them, a compound made of aluminum or a group 4A metal (for example, zirconium or titanium) in the periodic table is preferable. Particularly preferred is a water-soluble aluminum compound. As a water-soluble aluminum compound, for example, as an inorganic salt, aluminum chloride or a hydrate thereof, aluminum sulfate or a hydrate thereof, ammonium alum and the like are known. Furthermore, a basic polyaluminum hydroxide compound which is an inorganic aluminum-containing cationic polymer is known and preferably used.

The basic polyaluminum hydroxide compound has a main component represented by the following general formula 1, 2, or 3, for example, [Al ₆ (OH) ₁₅ ] ³⁺ , [Al ₈ (OH) ₂₀ ] ⁴⁺ , [Al ₁₃ (OH) ₃₄ ] ⁵⁺ , [Al ₂₁ (OH) ₆₀ ] ³⁺ , etc. is there.

[Al ₂ (OH) _n Cl _6-n ] _m General formula 1
[Al (OH) ₃ ] _n AlCl ₃ general formula 2
Al _n (OH) _m Cl _(3n-m) 0 <m <3n General formula 3

  These are water treatment agents from Taki Chemical Co., Ltd. under the name of polyaluminum chloride (PAC), from Asada Chemical Co., Ltd. under the name of polyaluminum hydroxide (Paho), and from Riken Green Co., Ltd. It is marketed under the name of Purachem WT and from other manufacturers for the same purpose, and various grades can be easily obtained.

  As the water-soluble compound containing a Group 4A element of the periodic table used in the present invention, a water-soluble compound containing titanium or zirconium is more preferable. Examples of the water-soluble compound containing titanium include titanium chloride and titanium sulfate. Water-soluble compounds containing zirconium include zirconium acetate, zirconium chloride, zirconium oxychloride, hydroxy zirconium chloride, zirconium nitrate, basic zirconium carbonate, zirconium hydroxide, zirconium lactate, zirconium carbonate / ammonium, zirconium carbonate / potassium, zirconium sulfate. And zirconium fluoride compounds. In the present invention, the term “water-soluble” means that 1% by mass or more dissolves in water at room temperature and normal pressure.

  As the binder for fixing these silica fine particles, a hydrophilic binder which is highly transparent and can obtain higher ink permeability is used. In using the hydrophilic binder, it is important that the hydrophilic binder does not swell at the initial permeation of the ink and block the gap. From this viewpoint, a hydrophilic binder having a low swelling property near room temperature is preferably used. .

  Polyvinyl alcohol, polyethylene glycol, starch, dextrin, carboxymethylcellulose, and the like are used, and particularly preferred hydrophilic binders are fully or partially saponified polyvinyl alcohol or cation-modified polyvinyl alcohol. Particularly preferred among polyvinyl alcohols are those having a degree of saponification of 80% or more or those that have been completely saponified, and the average degree of polymerization is preferably from 500 to 5,000.

  Examples of the cation-modified polyvinyl alcohol include polyvinyl alcohol having primary to tertiary amino groups and quaternary ammonium groups in the main chain or side chain as described in JP-A No. 61-10383. It is done.

In order to keep the void volume of the ink receiving layer in the range of 15 to 50 ml / m ² , the binder is preferably added in an amount of 5 to 25% by mass with respect to the silica fine particles, and the coating amount is 10 to 35 g / m ² as silica fine particles. Is more preferable, and a range of 13 to 30 g / m ² is more preferable.

  The ink receiving layer of the present invention may be applied by being divided into a plurality of layers having different types of silica fine particles, agglomeration density, primary particle diameter, binder blending amount, additives and the like as required. In this case, the void volume may be considered as the total void volume of a plurality of layers as long as there is no special obstacle such as permeation inhibition between the ink receiving layer layers.

  The ink-receptive layer of the present invention is a polyvalent metal compound, a cationic polymer, an antioxidant, a radical inhibitor, and an interface as a coating aid for the purpose of preventing cracking, improving ink fixability, and improving image storage stability. An activator, a water-soluble solvent, a viscosity adjuster, a pH adjuster, and the like can be appropriately added.

  Non-water-absorbent supports such as polyethylene, polypropylene, polyvinyl chloride, diacetate resin, triacetate resin, cellophane, acrylic resin, polyethylene terephthalate, polyethylene naphthalate, and polyolefin resin-coated paper Water-absorbing supports such as fine paper, art paper, coated paper and cast coated paper are used. Preferably, a non-water absorbing support is used. Among non-water-absorbing supports, polyolefin resin-coated paper is particularly preferable. The thickness of these supports is preferably about 50 to 250 μm.

  When a non-water-absorbing support such as a film or resin-coated paper is used as the support, a primer layer mainly composed of a natural polymer compound or a synthetic resin is preferably provided on the surface on which the ink receiving layer is provided. The primer layer provided on the support is mainly composed of natural polymer compounds such as gelatin and casein and synthetic resins. Examples of such synthetic resins include acrylic resins, polyester resins, vinylidene chloride, vinyl chloride resins, vinyl acetate resins, polystyrene, polyamide resins, polyurethane resins, and the like. The primer layer is provided on the support with a film thickness (dry film thickness) of 0.01 to 5 μm. Preferably it is the range of 0.01-2 micrometers.

  Various back coat layers can be coated on the support in the present invention for writing properties, antistatic properties, transport properties, anticurling properties and the like. The backcoat layer can contain an appropriate combination of inorganic antistatic agents, organic antistatic agents, hydrophilic binders, latexes, pigments, curing agents, surfactants, and the like.

  When the ink receiving layer coating solution is applied to a film support or resin-coated paper, corona discharge treatment, flame treatment, ultraviolet irradiation treatment, plasma treatment or the like is preferably performed prior to coating.

  In the present invention, a known coating method can be used as a coating method of each layer constituting the ink receiving layer. For example, there are a slide bead method, a curtain method, an extrusion method, an air knife method, a roll coating method, a rod bar coating method, and the like.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to an Example. In addition, unless otherwise indicated below, a part and% represent a mass part and the mass%, respectively.

<Preparation of polyolefin resin-coated paper support> Hardwood kraft pulp was beaten to 300 ml of Canadian Standard Freeness, cation-modified starch was 1.5% by weight of pulp, amphoteric polyacrylamide was 1.0% by weight of pulp, and sizing agent alkyl ketene 0.2% by weight of dimer and 0.2% by weight of polyamide polyamine epichlorohydrin were added to pulp, and the concentration was adjusted to 1% by weight to obtain a paper slurry. Next, this paper stock was prepared so as to have a basis weight of 170 g / m ² and a density of 1.06 g / cm ³ while giving an appropriate turbulence by a long paper machine, and a base paper of resin-coated paper was made.

First, the wire surface was subjected to corona discharge treatment while the base paper was running, and identification back printing was performed. Next, the wire surface was again subjected to corona discharge treatment, and the molten backside resin at 320 ° C. was extruded and coated at 20 g / m ² to form a rough surface-shaped back resin layer. Next, the felt surface of the base paper was subjected to corona discharge treatment, and the surface resin melted at 320 ° C. was extrusion-coated at 30 g / m ² to form a mirror-shaped surface resin layer. Furthermore, the back resin surface is treated with corona discharge to give an antistatic back coat coating solution as a solid content of 0.6 g / m ² , and the front resin surface is treated with corona discharge and the undercoat solution is applied at 50 mg / m ² , coated, dried and wound A polyolefin resin-coated paper support was produced.

<Containing back resin>
30 parts of low density polyethylene (density 0.920 g / cm ³ )
70 parts of high density polyethylene (density 0.967 g / cm ³ )

<Table resin blend>
15 parts of master batch (39.1 parts of low density polyethylene with a density of 0.918 g / cm ³ , 60 parts of surface-coated anatase type titanium oxide in terms of Al ₂ O ₃ , 0.9 parts of zinc stearate Kneading with a Banbury mixer)
85 parts of low density polyethylene (density 0.920 g / cm ³ )

<Backcoat coating liquid formulation>
Alkali hydrolyzate 25% solution of maleic anhydride polymer 4 parts Colloidal silica 20% slurry (Snowtex 20 manufactured by Nissan Chemical Industries, Ltd.) 20 parts Epoxy type crosslinker 10% solution 1.5 parts Sulfosuccinic acid-2- Ethylhexyl ester salt 5% solution 0.5 part The total amount was adjusted to 100 parts with water.

<Undercoat liquid formulation>
Lime-processed gelatin 2% aqueous solution 50 parts Sulfosuccinic acid-2-ethylhexyl ester salt 5% liquid 0.5 parts Chromium alum 5% aqueous solution 2 parts The total amount was adjusted to 100 parts with water.

An ink-receiving layer coating solution having the following composition was applied to the above support by a slide bead coater at a gas phase method silica conversion of 25 g / m ² and dried. When the cross section of the sample collected at this time was observed by TEM, the average secondary particle diameter of the silica fine particles was 80 nm, and the void volume was determined using a mercury porosimeter, and found to be 30 ml / m ² .

<Ink-receiving layer coating composition 1>
Gas phase method silica 20% slurry 60 parts (average primary particle size 7 nm)
Polydimethylallyl ammonium chloride 10% aqueous solution 2.4 parts Boric acid 10% aqueous solution 5.4 parts Polyvinyl alcohol 10% aqueous solution 27 parts (saponification degree 88%, average polymerization degree 3500)
Surfactant 5% aqueous solution The total amount was made up to 100 parts with 0.72 parts water.

Furthermore, a surface layer coating solution having the following composition is applied onto the ink receiving layer by using a slanted gravure roll having a diameter of 60 mm, a slanting angle of 45 degrees, a number of lines of 90 lines / inch, and a groove depth of 110 microns by reverse rotation and kiss touch. It was. The rotation speed of the oblique gravure roll was adjusted, and the coating was applied at a moisture application amount of 20 ml / m ² and dried. The amount of moisture applied was determined from the amount of coating liquid reduced per unit time during application, and the amount of solids applied was 0.2 g / m ² . Thus, the ink jet recording medium of Example 1 was obtained.
<Surface coating liquid formulation 1>
Colloidal silica 20% slurry, 5 parts (Quartron PL-3L, manufactured by Fuso Chemical Industry Co., Ltd.)
(Average primary particle size 35nm, coefficient of variation 0.11)
The total amount was 100 parts with water. (Silica concentration 1% by mass)

An ink jet recording medium of Example 2 was obtained in the same manner except that the surface layer coating solution formulation of Example 1 was replaced with the surface layer coating solution formulation 2.
<Surface coating liquid composition 2>
Colloidal silica 20% slurry 5 parts (Quartron PL-5, manufactured by Fuso Chemical Industry Co., Ltd.)
(Average primary particle size 55 nm, coefficient of variation 0.13)
The total amount was 100 parts with water. (Silica concentration 1% by mass)

An inkjet recording medium of Comparative Example 1 was obtained in the same manner except that the surface layer coating solution formulation of Example 1 was replaced with the surface layer coating solution formulation 3.
<Surface coating liquid composition 3>
Colloidal silica 20% slurry, 5 parts (Quartron PL-2L, manufactured by Fuso Chemical Industry Co., Ltd.)
(Average primary particle size 19 nm, coefficient of variation 0.11)
The total amount was 100 parts with water. (Silica concentration 1% by mass)

(Comparative Example 1)
An inkjet recording medium of Comparative Example 2 was obtained in the same manner except that the surface coating solution formulation of Example 1 was replaced with the surface coating solution formulation 4.
<Surface coating liquid formulation 4>
Colloidal silica 20% slurry 5 parts (Snowtex AKL manufactured by Nissan Chemical Industries, Ltd.
(Average primary particle size 45 nm, coefficient of variation 0.26)
The total amount was 100 parts with water. (Silica concentration 1% by mass)

(Comparative Example 2)
An inkjet recording medium of Comparative Example 2 was obtained in the same manner except that the surface coating solution formulation of Example 1 was replaced with the surface coating solution formulation 5.
<Surface coating liquid formulation 5>
Colloidal silica 40% slurry 2.5 parts (Snowtex OL40 manufactured by Nissan Chemical Industries, Ltd.
Average primary particle size 43nm, coefficient of variation 0.20))
The total amount was 100 parts with water. (Silica concentration 1% by mass)

(Comparative Example 3)
An inkjet recording medium of Comparative Example 2 was obtained in the same manner except that the surface layer coating solution formulation of Example 1 was replaced with the surface layer coating solution formulation 6.
<Surface coating liquid composition 6>
Colloidal silica 40% slurry 2.5 parts (Snowtex OZL manufactured by Nissan Chemical Industries, Ltd.
(Average primary particle size 80nm, coefficient of variation 0.31)
The total amount was 100 parts with water. (Silica concentration 1% by mass)

(Comparative Example 4)
In Example 1, an ink jet recording medium comprising only an ink receiving layer was obtained without applying the surface layer.

<Evaluation of inkjet recording medium>
These ink jet recording media were evaluated as follows after aging at 50 ° C. for 24 hours under hermetically sealed packaging.
<Ink Absorption> After the humidity of the ink jet recording medium was adjusted to 23 ° C. and humidity 55% RH day and night, blue solid printing was performed with an ink jet printer PM-980C manufactured by Seiko Epson Corporation under the same conditions. Since the bronzing phenomenon (the print surface becomes reddish purple when observed under oblique light) occurs when the ink absorbability is poor, the determination was made based on the presence or absence of this phenomenon.
○: No bronzing phenomenon observed.
Δ: A slight bronzing phenomenon is observed.
X: A bronzing phenomenon is observed.

<Glossiness> The gloss of an unprinted portion of the inkjet recording medium was visually determined.
○: Exceeds photographic printing paper (glossy) and is extremely glossy.
Δ: Photographic paper (glossy) level.
X: Slightly lower than photographic paper (glossy).

<Print part haze> The ink jet recording medium was conditioned at 23 ° C. and a humidity of 55% RH all day and night, and under the same conditions, black solid printing was performed with an ink jet printer PM-980C manufactured by Seiko Epson Corporation. When the print portion was observed with oblique light, when the print portion haze was generated, a thin cloudiness was observed on the surface, and thus the determination was made based on the presence or absence of this phenomenon.
O: Print haze generation is extremely low and is hardly observed.
Δ: Slight generation of print portion haze is observed.
X: Print portion haze is observed.

  In any of the ink jet recording media of the examples, the bronzing phenomenon and the print portion haze associated with the deterioration of the ink absorbability are not observed or are practically satisfactory, and the gloss is excellent. The ink jet recording material of the comparative example is inferior in any of ink absorptivity, gloss, and print portion haze.

Claims (1)

  In an inkjet recording material having a porous ink receiving layer mainly composed of silica fine particles having an average secondary particle diameter of 500 nm or less and a surface layer mainly composed of colloidal silica on the support, the colloidal silica is averaged An ink jet recording material comprising monodisperse colloidal silica having a primary particle size of 80 nm or less and a coefficient of variation of 0.15 or less.