JP2012213924A - Ink jet recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording medium which has high printing density and ink absorbency, further has satisfactory printer aptitude that an ink driving amount for commercial application is reduced.SOLUTION: In the ink jet recording medium in which at least either side of a paper support having air permeability is provided with an ink receptive layer with a coating amount of 3 to 8 g/mincluding synthetic amorphous silica and polyvinyl alcohol by a coagulation cast coating method, Cobb water absorptiveness (30 s) to distilled water specified in JIS P 8140 on the ink receptive layer face side is controlled to 15 to 30 g/m.

Description

  The present invention relates to an inkjet recording medium having gloss suitable for an inkjet recording system.

  The ink jet recording method is a recording method in which fine droplets of ink ejected by various methods are attached to a recording paper such as paper to form an image or characters. This recording system is widely used for home use because it is easy to increase the speed and full color, and has low noise during recording and a low-cost apparatus.

  On the other hand, in the field of commercial use, conventionally, variable information (such as utility bills, credit bills, receipts, delivery slips, advertisements, etc.) has been printed using an electrophotographic non-impact printer (NIP). However, in recent years, it has been replaced with printing by a high-speed ink jet printer having a line head, which is excellent in printing speed. Since commercial printers perform high-speed printing, a small amount of ink is applied, and therefore, a certain amount of ink needs to be spread due to the physical properties of paper.

  By the way, the ink jet recording paper is roughly classified into a coated paper type provided with an ink receiving layer containing a pigment and a plain paper type not provided with an ink receiving layer containing a pigment. The coated paper type that can reproduce high-definition images is mainly used for digital camera image output, while the cheap plain paper type is mainly used for printing business reports, utility bills, and transfer paper. It is done.

  Of these coated paper types, glossy paper has been demanded in recent years from a high-class perspective.

  Up to now, glossy inkjet recording media have been widely used for home use, and are generally manufactured by a cast coating method using a cast coater from the viewpoint of manufacturing cost.

  The cast coating method is a method in which a coating liquid mainly composed of a pigment and a binder is coated on a support to provide a coating layer, and the coating layer is gloss-finished using a cast drum. The gloss coating layer becomes the ink receiving layer. The cast coating method includes (1) a wet casting method (direct method) in which a coating layer is pressed onto a mirror-finished heating drum while the coating layer is wet, and (2) a wet coating layer is once dried. Or a rewetting method in which it is semi-dried and then swelled and plasticized with a rewetting liquid, pressed onto a mirror-finished heated drum and dried, and (3) a heated drum in which the wet coating layer is gelled by coagulation and then mirror-finished There are generally known three types of gelation cast methods (coagulation methods) in which pressure is bonded to the substrate and dried. The principle of each method is the same in that the wet coating layer is pressed against the mirror-finished surface to give gloss to the coating layer surface.

The quality characteristics required for such a glossy inkjet recording medium include high gloss on the surface of the recording medium, high print density, no ink overflow or bleeding, and uneven printing (light / dark unevenness). And a method for producing a high-quality inkjet recording paper satisfying these characteristics by a cast coating method has been already proposed (Patent Document 1, Patent Document 2, (Patent Document 3, Patent Document 4, etc.)
Japanese Patent Laid-Open No. 2-27487 Japanese Patent Laid-Open No. 9-263039 JP-A-2005-35169 JP 2002-166645 A

  However, in the case of the techniques described in Patent Documents 1 to 4, since the inkjet printer for household use is targeted, a printer with a small amount of ink for commercial use has a portion where the ink has not spread sufficiently and has been whitened into the printing unit. There is a problem that occurs.

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an ink jet recording medium that is excellent in glossiness and secures a suitable ink spread in a commercial printer while obtaining a high print density.

  As a result of various studies, the present inventors have found that when the ink receiving layer is provided by the coagulation cast coating method, the above problems can be solved by adjusting the ink absorption by the coating amount and maintaining high glossiness and printing density. The headline and the present invention were reached.

  In addition, as a result of various investigations on an appropriate method for evaluating the spread of ink in a printer for commercial use, it has been found that the evaluation can be performed by the Cobb water absorption (30 seconds) defined by JIS P 8140.

That is, the inkjet recording medium of the present invention is an ink having a coating amount of 3 to 8 g / m ² containing synthetic amorphous silica and polyvinyl alcohol on at least one side of a paper support containing air permeability. In the ink jet recording medium in which the receiving layer is provided by the coagulation cast coating method, the Cobb water absorption (30 seconds) with respect to distilled water as defined in JIS P 8140 on the ink receiving layer surface side is 15 g / m ² or more and 30 g / m ² or less. It is adjusted.

  The ink receiving layer preferably contains cationic colloidal silica having an average particle size of 5 nm to 80 nm.

  According to the present invention, an ink jet recording medium having an excellent gloss feeling, a high print density when ink jet recording is performed using a dye ink of a commercial printer, and further ensuring an appropriate ink absorbability and an excellent operability can be obtained. It is done.

  Embodiments of the present invention will be described below. In the ink jet recording medium of the present invention, a coating layer containing a pigment and a binder is formed on at least one surface of a gas-permeable support, and then the binder is solidified on the surface of the coating layer. A coagulant is applied and an ink receiving layer is provided by a coagulation cast coating method.

(Base paper)
As the base paper used in the present invention, any material can be used as long as it has a gas permeability sufficient to transmit water vapor generated in the cast drum during cast coating. Etc. is preferably used. The base paper is composed of pulp fibers and fillers. The raw material pulp includes chemical pulp (conifer bleached or unbleached kraft pulp, hardwood bleached or unbleached kraft pulp, etc.), mechanical pulp (ground pulp, thermomechanical pulp, Chemi-thermomechanical pulp, etc.), deinked pulp, etc. can be used alone or mixed in any proportion. It is preferable that softwood pulp is contained as the raw material pulp. When softwood pulp is blended in the base paper, the strength of the base paper is improved and the glossiness of the ink receiving layer tends to be improved. However, since the surface property of the base paper tends to decrease when the content of softwood pulp increases, the content of softwood pulp is preferably 30% by mass or less in the total pulp. The pH of the base paper may be acidic, neutral or alkaline. The filler can be appropriately selected from known fillers such as hydrated silicic acid, white carbon, talc, kaolin, clay, calcium carbonate, titanium oxide, and synthetic resin fine particles.

  From the viewpoint of production efficiency of the ink jet recording medium, the air permeability of the base paper is preferably 500 seconds or less, and from the viewpoint of coating properties, the Steecht sizing degree of the base paper is preferably 30 seconds or more. .

  In addition, for the above support, a liquid containing various additives including a water-soluble polymer additive is used as an on-machine or off-machine using a tab size, a size press, a gate roll coater, a film transfer coater, or the like. It is possible to apply with.

  Examples of the water-soluble polymer additive include starch derivatives such as starch, cationized starch, oxidized starch, etherified starch, and phosphate esterified starch; polyvinyl alcohol derivatives such as polyvinyl alcohol and carboxy-modified polyvinyl alcohol; carboxymethyl cellulose, Cellulose derivatives such as hydroxymethylcellulose, hydroxyethylcellulose, cellulose sulfate, etc .; water-soluble natural polymers such as gelatin, casein, soybean protein; sodium polyacrylate, sodium styrene-maleic anhydride copolymer, sodium polystyrenesulfonate, etc., anhydrous Water-soluble polymers such as maleic acid resins; aqueous polymer adhesives such as thermosetting synthetic resins such as melamine resins and urea resins are used. Other additives include petroleum resin emulsion, styrene-maleic anhydride copolymer alkyl ester ammonium salt, alkyl ketene dimer emulsion, styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, polyethylene as sizing agent. And dispersion such as polyvinylidene chloride. Examples of other additives include sodium chloride, calcium chloride, and bow glass that are inorganic electrolytes as antistatic agents, and glycerin, polyethylene glycol, and the like as hygroscopic substances. Examples of other additives include clay, kaolin, talc, barium sulfate, and titanium oxide as pigments. As other additives, hydrochloric acid, caustic soda, sodium carbonate, etc. are used as pH adjusters, and other additives such as dyes, fluorescent brighteners, antioxidants, ultraviolet absorbers, etc. can be used in combination. is there.

(Pigment of ink receiving layer)
As the pigment of the ink receiving layer (the coating layer is made into an ink receiving layer by a coagulation cast coating method, but for convenience, the coating layer and the ink receiving layer are used without distinction), a known inorganic fine particle or organic fine particle is used. Can be used. Examples of the pigment include synthetic amorphous silica, colloidal silica, aluminum hydroxide, alumina hydrate (alumina sol, colloidal alumina, pseudoboehmite, etc.), alumina (α type crystal alumina, θ type crystal alumina, γ type) Crystal alumina, etc.), kaolin, talc, calcium carbonate, titanium dioxide, clay, zinc oxide and the like can be used. These can be used alone or in combination of two or more, but it is essential that the pigment contains synthetic amorphous silica in terms of printing density and ink absorbability.

(Binder for ink receiving layer)
As a binder for the ink receiving layer, polyvinyl alcohol, which is a water-based binder resin, is essential from the viewpoint of the strength of the coating layer. Other water-based binder resins are also blended as necessary to ensure the coating layer strength. The “aqueous system” means that the resin is dissolved or dispersed and stabilized (water-soluble or / and water-dispersible resin emulsion) in water or a medium composed of water and a small amount of an organic solvent. The aqueous binder resin means a water-soluble resin and a water-dispersible resin. The aqueous binder resin is dissolved or dispersed in the coating liquid to be coated on the support, but after coating and drying, it becomes a binder for the pigment and forms an ink receiving layer.

  Examples of other aqueous binder resins include polyvinyl pyrrolidone; urethane resins derived from urethane resin emulsions; starches such as oxidized starch and esterified starch; cellulose derivatives such as carboxymethyl cellulose and hydroxyethyl cellulose; casein; gelatin; soy protein; -Acrylic resin and derivatives thereof; styrene-butadiene resin latex; acrylic resin emulsion, vinyl acetate resin emulsion, vinyl chloride resin emulsion, urea resin emulsion, alkyd resin emulsion, and derivatives thereof. These aqueous binder resins can be used by mixing with polyvinyl alcohol.

(Polyvinyl alcohol)
In the present invention, the polyvinyl alcohol is preferably partially saponified polyvinyl alcohol. The addition amount of polyvinyl alcohol is preferably 5 to 30 parts by mass with respect to 100 parts by mass of the total pigment in the ink receiving layer. However, the type of the binder is not particularly limited as long as the required coating layer strength is obtained.

(Synthetic amorphous silica)
The synthetic amorphous silica can be roughly classified into wet method silica and gas phase method silica depending on the production method. Synthetic amorphous silica produced by a wet process is inferior to gas phase process silica in pigment transparency, but is excellent in paint stability when used in combination with polyvinyl alcohol. Furthermore, wet process silica has better dispersibility than gas phase process silica without internal voids, and can increase the coating concentration. Therefore, the ratio of the pigment (to the binder) in the ink receiving layer can be increased, and the absorbability of the ink receiving layer can be increased, so that the ink absorbability can be improved and the color developability of the dye ink can be improved. The average secondary particle diameter of the wet process silica is preferably 1 to 5 μm, and the BET specific surface area is preferably 100 to 400 m ² / g from the viewpoint of obtaining a high gloss feeling. Further, from the viewpoint of obtaining a coating layer with high transparency, the vapor phase silica preferably has an average primary particle diameter of 4 nm to 30 nm, and a BET specific surface area of 100 to 400 m ² / g.

  When two or more kinds of pigments having different average particle diameters are used as the pigment of the ink receiving layer, the “average pigment particle diameter” is a value obtained by weighted averaging the average particle diameter of each pigment by the content ratio of each pigment. To do. The average particle size of the pigment in the ink receiving layer is preferably 1 to 5 μm. If it is smaller than 1 μm, the ink absorbency is inferior, and if it exceeds 5 μm, the glossiness tends to decrease.

  The ink receiving layer contains the above-described pigment and binder, but other components such as a thickener, an antifoaming agent, an antifoaming agent, a pigment dispersant, a release agent, a foaming agent, a pH adjusting agent, and a surface. Sizing agent, coloring dye, coloring pigment, fluorescent dye, ultraviolet absorber, antioxidant, light stabilizer, preservative, water resistance agent, dye fixing agent, surfactant, wet paper strength enhancer, water retention agent, cation In the range which does not impair the effect of this invention, a conductive polymer electrolyte etc. can be suitably added to the coating layer used as an ink receiving layer.

  As a method of applying a coating liquid to be an ink receiving layer on a support, blade coater, air knife coater, roll coater, brush coater, kiss coater, squeeze coater, curtain coater, die coater, bar coater, gravure coater, gate roll A known coating machine such as a coater or a short dwell coater can be appropriately selected from the coating methods used on-machine or off-machine.

(Amount of ink receiving layer)
The coating amount of the ink receiving layer is required to be 3 g / m ² or more to cover the surface of the support, and the portion that has been whitened out in the solid printing portion with a suitable ink spread in a commercial printer. In order to adjust so that the ink does not overflow, it is changed as appropriate. However, in consideration of productivity, it is preferably 8 g / m ² or less. If it exceeds 8 g / m ² , the drying load increases, causing a reduction in the coating speed and lowering the productivity. In addition, since it becomes a price competing with general coated paper for commercial use, a coating cost exceeding 8 g / m ² leads to a decrease in competitiveness. Accordingly, it is essential that the coating amount of the ink receiving layer is 3 g / m ² or more and 8 g / m ² or less.

(Formation of ink receiving layer)
In the present invention, gloss is imparted by forming the outermost ink receiving layer by a solidified cast coating method. The coagulation cast coating method is performed as follows, for example. First, a coating liquid to be an ink receiving layer is applied to a support. Next, an aqueous solution for coagulation having a function of coagulating a binder (particularly an aqueous binder) in the coating liquid is applied to an undried coating layer and gelled, and then heated to a mirror-finished surface. Crimp and dry. The coagulation cast coating method can provide the ink receiving layer with a surface feel and gloss comparable to silver salt photography.

  If the coating layer is in a dry state when applying the aqueous solution for coagulation, it is difficult to copy the mirror drum surface, and the surface of the resulting ink-receiving layer will have many fine irregularities, giving it the same glossiness as a silver salt photograph. Hateful. After applying the aqueous solution for solidification while the coating layer is in a wet state, the surface of the coating layer is brought into contact with the heated mirror-finished surface to give gloss. In particular, when polyvinyl alcohol is used as the water-based binder, the ink receiving layer can be given a good gloss feeling by being coagulated using a boron compound as a coagulant, and the operability is also improved. However, when cationic colloidal silica is added, the borate cannot be used because it causes shock and aggregation with the borate.

(Coagulation method)
In the present invention, the coagulation method includes coagulation by polyvinyl alcohol in the ink receiving layer coating solution and a boron compound (boric acid) in the coagulating aqueous solution, a high pH of the ink receiving layer coating solution, and a low pH of the coagulating aqueous solution. By the coagulation by the agglomeration reaction, an ink receiving layer having high gloss can be provided, and stable operation can be performed. The method for applying the aqueous solution for coagulation is not particularly limited as long as it can be applied to the coating layer, and can be appropriately selected from known methods (for example, roll method, spray method, curtain method, etc.).

(Components of aqueous solution for coagulation)
The coagulant used in the present invention contains, in addition to the boron compound, a cationic resin, cationic colloidal silica, and a release agent.

(Cationic colloidal silica)
When cationic colloidal silica is contained in the coagulant, the cationic colloidal silica adheres to (is present on) the surface of the ink receiving layer due to cast coating. Since colloidal silica has a relatively small average particle size, the printing density of the dye ink is improved. Further, since colloidal silica having a small average particle diameter is present on the outermost surface of the ink receiving layer, the surface of the ink receiving layer becomes smooth and the glossiness is improved.

  Furthermore, since colloidal silica is cationic, even if a cationic resin and cationic colloidal silica, which will be described later, coexist in the coagulant, both do not aggregate and the coagulant can be stably applied. .

  Cationic colloidal silica is colloidal silica whose particle surface is highly positively charged. Cationic colloidal silica is a polyvalent metal such as aluminum ion, magnesium ion, calcium ion, zirconium ion, etc. on colloidal silica obtained by heating and aging silica sol obtained through metathesis or acid exchange resin layer of sodium silicate, for example. Obtained by reacting ions. For example, Japanese Patent Publication No. 47-26959 discloses cationic colloidal silica by aluminum treatment.

  Examples of commercially available cationic colloidal silica include LUDOX CL and LUDOX CL-P manufactured by Grace. In the present invention, two or more kinds of cationic colloidal silica may be mixed and used.

  From the viewpoint of improving the glossiness and transparency of the ink receiving layer, the average particle size of the cationic colloidal silica is preferably in the range of 5 nm to 80 nm. When the average particle size of the cationic colloidal silica is smaller than 5 nm, the glossiness of the coating layer is excellent, but the absorbability of the dye ink may be inferior. On the other hand, if the average particle size of the cationic colloidal silica is larger than 80 nm, the transparency of the coating layer may be lowered, and the printing density of the dye ink may be lowered. Further, two or more types of cationic colloidal silica having different average particle diameters may be used in combination.

  Further, from the viewpoint of smoothing the outermost surface of the ink receiving layer and improving the glossiness, the average primary particle diameter of the cationic colloidal silica is smaller than the average particle diameter (weighted average particle diameter) of the pigment of the ink receiving layer. preferable. In this way, the finest cationic colloidal silica covers the outermost surface of the ink receiving layer, so that the glossiness is improved.

  When two or more kinds of cationic colloidal silica having different average particle diameters are used, the “primary particle diameter of the cationic colloidal silica” means the average particle diameter of each cationic colloidal silica and the content ratio of each cationic colloidal silica. The weighted average value. Similarly, when two or more kinds of pigments having different average particle diameters are used as the pigment of the ink receiving layer, the “primary particle diameter of the pigment” is a value obtained by weighted averaging the average particle diameter of each pigment by the content ratio of each pigment. And

  The primary particle diameter of colloidal silica can be measured by, for example, a light intensity distribution analysis type particle diameter distribution measuring apparatus.

  Moreover, it is preferable that the compounding quantity of the cationic colloidal silica in a coagulant shall be 0.5 mass%-10 mass%. When the blending amount of the cationic colloidal silica is less than 0.5% by mass, the glossiness and the effect of improving the printing density of the dye ink may not be obtained. On the other hand, when the amount of the cationic colloidal silica is more than 10% by mass, aggregates may be generated and the stability of the coagulant may be lowered.

(Cationic resin)
When a cationic resin is included in the coagulant, the cationic resin adheres to (is present on) the surface of the ink receiving layer due to cast coating. The cationic resin fixes the ink and improves the print density and water resistance.

Examples of the cationic resin include polyamine sulfone, polyalkylene polyamine, polyamine condensate, polyallylamine, polydiallylamine, polyvinylamine, polyethyleneimine, dicyandiamide condensate, cationic acrylic resin, and cationic urethane resin. Species or multiple species can be selected and used.
(Release agent)
Moreover, it is necessary to add a release agent to the coating layer and / or the coagulant as necessary. The melting point of the release agent is preferably 90 to 150 ° C, and particularly preferably 95 to 120 ° C. In the above temperature range, the melting point of the release agent is almost equal to the temperature of the mirror finish surface, so that the ability as a release agent is maximized. The release agent is not particularly limited as long as it has the above properties, but it is preferable to use polyethylene-based and paraffin-based wax emulsions.
In the present invention, it has been found that the ink spread (ink absorbency) required for a printer for general commercial use correlates with the measurement result of the Cobb water absorption (30 seconds) with respect to distilled water specified by JIS P 8140. Yes. In the present invention, it is essential that the Cobb water absorption is 15 g / m ² or more and 30 g / m ² or less. When the Cobb water absorption is less than 15 g / m ² , the ink overflows, and when it exceeds 30 g / m ² , a phenomenon occurs in which the solid print portion is whitened.

In order to adjust the Cobb water absorption within this range, it is determined to some extent by the types and blending amounts of the synthetic amorphous silica and polyvinyl alcohol blended in the ink receiving layer, and it is preferable to finely adjust the coating amount.
In the present invention, a back coat layer having various functions such as ink absorptivity, writing property, printer printability and the like may be further provided on the opposite side.

  The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these examples. “Part” and “%” represent “part by mass” and “% by mass”, respectively, unless otherwise specified.

[Example 1]
Rosetta-type light calcium carbonate (trade name) as a filler for pulp slurry of Canada standard freeness (CSF) 400ml consisting of 90 parts hardwood bleached kraft pulp (L-BKP) and 10 parts softwood bleached kraft pulp (N-BKP) : Albuquer 5970, manufactured by SMI) to an ash content of 10%, 1.0 part of aluminum sulfate, 0.2 part of alkyl ketene dimer (AKD), and 0.5 part of a yield improver were added. The slurry is used to make a paper with a paper machine. At that time, a coating liquid containing starch having a solid content concentration of 5% and a surface sizing agent (AKD) having a solid content concentration of 0.2% is applied in a solid content of 1%. the coating is .5g / ^{m 2,} to obtain a paper support of 180 g / ^{m 2.}
The coating liquid A was applied to this paper support with a roll coater so that the coating amount was 3 g / m ^{2 in} terms of solid content. While this coating layer is in a wet state, the coagulant solution B is applied and solidified to a solid content of 2 g / m ² and then applied to a mirror-finished surface heated via a press roll. The mirror surface was copied by pressure bonding, and an ink jet recording medium of 185 g / m ² was obtained.
<Coating fluid A>
Colloidal silica (trade name: Quatron PL-3, manufactured by Fuso Chemical Industry Co., Ltd., average primary particle size 30 nm) as a pigment, gas phase synthetic amorphous silica (trade name: Aerosil 200V, manufactured by Nippon Aerosil Co., Ltd.) , 10 parts of an average primary particle diameter of 12 nm) and 70 parts of a wet process synthetic amorphous silica (trade name: Fine Seal X-37, manufactured by Tokuyama Corporation, average secondary particle diameter of 2.3 μm), and polyvinyl as a binder. 12 parts of alcohol (trade name: PVA217, manufactured by Kuraray Co., Ltd.), 1.5 parts of fluorescent dye (trade name: BLANKOPHOR P liquid01, manufactured by LANXESS), release agent (trade name: Meikatex HP68, Meisei Chemical Co., Ltd.) 0.5 parts, 0.1 parts of antifoaming agent (trade name: SN deformer 480, manufactured by San Nopco Co., Ltd.) and a coating solution having a concentration of 25% and a pH of 8.5. Sei was.
<Coagulant solution B>
Boric acid 4%, cationic resin (trade name: Saftomer ST3300, manufactured by Mitsubishi Chemical Corporation) 1%, cationic colloidal silica (trade name: LUDOX CL-P, manufactured by Grace, average primary particle size 22 nm) 0.5 %, Release agent (trade name: Meikatex HP68, manufactured by Meisei Chemical Co., Ltd.) 0.5 part, antifoaming agent (trade name: SN deformer 480, manufactured by San Nopco Co., Ltd.) 0.1%, pH 3 A coagulant solution was prepared.

[Example 2]
An ink jet recording medium was obtained in the same manner as in Example 1 except that the amount of the cationic colloidal silica in the coagulant solution B was changed to 7%.

[Example 3]
An ink jet recording medium was obtained in the same manner as in Example 1 except that the amount of the cationic colloidal silica in the coagulant solution B was changed to 10%.

[Example 4]
An ink jet recording medium was obtained in the same manner as in Example 1 except that the cationic colloidal silica of the coagulant solution B was changed to LUDOX CL (produced by Grace, average primary particle diameter: 12 nm).

[Example 5]
An ink jet recording medium was obtained in the same manner as Example 1 except that the coating liquid A was changed to 1 g / m ² in terms of solid content.

[Example 6]
An ink jet recording medium was obtained in the same manner as in Example 1 except that the coating liquid A was changed to 6 g / m ² in terms of solid content.

[Comparative Example 1]
An ink jet recording medium was obtained in the same manner as in Example 1 except that the coating liquid A was changed to 7 g / m ² in terms of solid content.

[Comparative Example 2]
An ink jet recording medium was obtained in the same manner as in Example 1 except that the coating liquid A was changed to a solid content and the coating amount was changed to 0.5 g / m ² .

[Comparative Example 3]
An ink jet recording medium was obtained in the same manner as in Example 1 except that the amount of the cationic colloidal silica in the coagulant solution B was changed to 12%.

[Comparative Example 4]
An ink jet recording medium was obtained in the same manner as in Example 1 except that the synthetic amorphous silica of the coating liquid A was changed to kaolin (trade name: Capim DG, manufactured by Rio Capim).

[Comparative Example 5]
An inkjet recording medium was obtained in the same manner as in Example 1 except that the synthetic amorphous silica of the coating liquid A was changed to light calcium carbonate (trade name: TP-121, manufactured by Okutama Kogyo Co., Ltd.).

[Comparative Example 6]
Except that the synthetic amorphous silica of the coating liquid A was not blended and was changed to 100 parts of colloidal silica (trade name: Quatron PL-3, manufactured by Fuso Chemical Industries, Ltd., average primary particle size 30 nm). In the same manner as in Example 1, an ink jet recording medium was obtained.

(Evaluation)
The following items were evaluated for the ink jet recording media obtained in Examples and Comparative Examples, and the results are shown in Table 1.

1. Print density
Four colors of cyan, magenta, yellow, and black were printed on the obtained inkjet recording medium using a dye inkjet printer (PM-970C, mode: EPSON photo paper / clean, manufactured by Epson Corporation). If the total value of four colors is 8.5 or more, there is no practical problem.

2. Solid image (simple evaluation of commercial printer suitability)
Black and green solids are printed on the obtained ink jet recording medium using a dye ink jet printer (MJ-6000C, mode: exclusive glossy paper / standard, manufactured by Epson Corporation), and white portions and blurring of the solid portions are printed. Evaluated.
○: A clear image without white spots and blurring.
X: There are white spots or bleeding.

3. 20 ° glossiness
The 20 ° glossiness of the unprinted portion on the surface of the ink receiving layer of the obtained inkjet recording medium was measured according to JIS-Z8741. It measured using the glossiness meter (Murakami Color Research Laboratory make, True GLOSS GM-26PRO). If the 20 degree glossiness is 20% or more, there is no practical problem.

4). Stability of the ink receiving layer coating solution and the aqueous solution for coagulation After the preparation, the solution was allowed to stand for 24 hours, and the presence or absence of aggregates was visually evaluated. If the evaluation is Δ or more, there is no practical problem.
○: There is an aggregate.
Δ: There are fine aggregates.
X: There is no aggregate.

5. Coatability If the following continuous operability is Δ or more and the following coating speed is 30 m / min or more, there is no practical problem.
5-1 Continuous operability The cloudiness of the cast drum after continuous coating of 20,000 m was visually observed and evaluated according to the following criteria.
◎: No fogging on the drum surface at all ○: Slight fogging on the drum surface can be confirmed, but there is almost no problem with suitability for long run △: Cloudiness on the drum surface can be confirmed, and there is a problem level ×: Entire surface of the drum surface 5-2 Coating speed with much fogging confirmed The maximum speed at which no defects occur on the glossy surface is evaluated, and if it is 30 m / min or more, there is no practical problem.

6). Cobb water absorption (30 seconds)
The surface of the ink receiving layer was measured for Cobb water absorption (30 seconds) according to JIS P 8140.

表１から明らかなように、実施例１〜６の本発明のインクジェット用紙では光沢度および印字濃度に優れ、コッブ吸水度を１５〜３０ｇ／ｍ^２の範囲とすることで商業用途の高速プリンターに対応したインク吸収性が得られた。
一方、コッブ吸水度の範囲から外れた比較例１〜６は商業用途の高速プリンターのいてはインク吸収性が劣り、比較例４〜５は光沢度および印字濃度にも劣っていた。

As is apparent from Table 1, the inkjet papers of the present inventions of Examples 1 to 6 are excellent in glossiness and print density, and have a Cobb water absorption in the range of 15 to 30 g / m ² to achieve a commercial high-speed printer. Corresponding ink absorbency was obtained.
On the other hand, Comparative Examples 1-6, which deviated from the range of Cobb water absorption, were inferior in ink absorbency for high-speed printers for commercial use, and Comparative Examples 4-5 were also inferior in glossiness and print density.

Claims (3)

An ink receiving layer containing 3 to 8 g / m ² of a coating containing synthetic amorphous silica and polyvinyl alcohol was provided on at least one surface of a paper support containing air permeability by a coagulation cast coating method. An ink jet recording medium having a Cobb water absorption (30 seconds) with respect to distilled water defined by JIS P 8140 on the ink receiving layer surface side of 15 g / m ² or more and 30 g / m ² or less.   2. The ink jet recording medium according to claim 1, wherein the ink receiving layer contains cationic colloidal silica having an average particle diameter of 5 nm to 80 nm.   After providing a coating layer containing synthetic amorphous silica and polyvinyl alcohol on at least one surface of a gas-permeable support, a cationic colloid having an average particle size of 5 nm to 80 nm on the surface of the coating layer An inkjet recording medium in which a coagulant solution containing silica, boric acid, and a cationic resin is applied and an ink receiving layer is provided by a coagulation cast coating method, and the cationic colloidal silica contained in the coagulant The ink jet recording medium according to claim 1, wherein the boric acid and the cationic resin are present on the surface of the ink receiving layer.