JP2009073158A - Recording medium, its manufacturing process, and ink-jet recording method using this recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording medium in which printing of high quality equivalent to offset printing can be executed at a low cost and a high speed, and to provide an ink-jet recording method using this recording medium. <P>SOLUTION: In the recording medium of this invention, which recording medium is composed by sequentially laminating a stencil, a first layer including a binder, and a second layer including a white pigment; the stencil provided with the first layer has a cop water-absorbing capacity for 15 sec of a contact time according to a water-absorbing capacity test stipulated in JIS P8140 of 5.0 g/m<SP>2</SP>or less, and the second layer has the water-absorbing amount for 0.5 sec of a contact time according to a Bristow's process of 2 mL/m<SP>2</SP>or more to 8 mL/m<SP>2</SP>or less. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a recording medium, a method for manufacturing the recording medium, and an ink jet recording method using the recording medium.

  The ink jet apparatus has a simple configuration, and high-quality image recording can be performed by ink jet recording performed using the ink jet apparatus. The ink used in the inkjet recording is designed to have a viscosity of about several mPa · s to 30 mPa · s and a surface tension of about 20 mN / m to 40 mN / m so that the ink can be ejected from the inkjet head.

  Usually, the ink contains 50% by mass to 90% by mass of an ink solvent so that the viscosity of the ink falls within the above range. As the ink solvent, water, an organic solvent, oil, a photopolymerizable monomer, and the like are used. In particular, water is frequently used from the viewpoint of environmental suitability. In addition, the ink solvent generally contains a high-boiling solvent such as glycerin so that the discharge nozzle of the ink jet head does not cause clogging due to drying of the ink solvent.

  On the other hand, image blur due to a large amount of ink solvent and color mixing between colors occur in a recording medium on which ink is drawn. For this reason, image blurring or color mixing between colors occurs when an ink jet exclusive paper (FIG. 5) having a solvent absorbing layer (ink receiving layer) of about 20 to 30 μm on the surface for absorbing the ink solvent is used as a recording medium. Is suppressed.

  Further, in the case of water-based ink using water as an ink solvent, paper permeation such as curl or cockle occurs when water penetrates into the base paper during recording. However, as shown in FIG. When the solvent absorption layer 22 is formed on the paper, it is possible to suppress the penetration of water into the base paper and suppress the paper deformation.

  On the other hand, when forming a graphical image with high image density and image area ratio, the amount of ink per unit area on the recording medium increases, and the solvent absorption layer cannot suppress the penetration of the ink solvent into the base paper. Therefore, water-resistant paper (for example, laminate paper) including a water-resistant layer such as a polyolefin layer is used (see, for example, Patent Documents 1 and 2).

  Ink jet technology has been applied to fields such as office printers and home printers, but has recently been applied in the field of commercial printing. This commercial printing field does not have a photo-like surface that completely shuts out the penetration of the ink solvent into the base paper, but requires a printing texture like general-purpose printing paper. Here, when the solvent absorption layer in the recording medium is as thick as 20 to 30 μm, the surface gloss, texture, stiffness, etc. of the recording medium are limited. However, it is limited to posters, form printing, and the like that are allowed to be restricted in terms of surface gloss, texture, stiffness, etc. Further, the recording medium has a high cost due to the solvent absorption layer and the water resistant layer, which also contributes to the above limitation.

Further, in Patent Document 3, at least a lower layer and an upper layer are provided on a support and manufactured by casting, the lower layer contains a water-absorbing inorganic pigment, a latex binder, boric acid or a salt thereof, and the upper layer It contains submicron pigment and polyvinyl alcohol, and after obtaining a state where the pH of the upper layer surface is 8 or higher, it is treated using an acid-containing liquid so that the pH of the upper layer surface is 5.5 or lower. A method for manufacturing an inkjet recording medium is disclosed.
However, in Patent Document 3, since the ability of the blocking layer to block water is not sufficient, when an image is formed with ink, the water in the ink passes through the blocking layer and reaches the base paper, causing cockling and curling. Further, since the surface pH before pH adjustment is as high as 8, and even if the pH is adjusted to be low with an acid, it has a buffering capacity, so that the aggregation of the coloring material dissolved or dispersed in the ink is slow, and image bleeding and landing There is a problem in that the image quality is deteriorated due to deformation of the subsequent droplet ejection.

Patent Document 4 discloses a recording paper for recording using an aqueous recording liquid containing a dye that changes from water-soluble to water-insoluble due to a change in pH, which is neutral paper, and the surface pH of the recording paper is described above. There has been proposed a recording paper in which the dye is adjusted to a pH value or less at which the dye becomes water-insoluble.
Patent Document 5 discloses that a recording paper recorded with an ink using a water-soluble dye mainly having a carboxyl group as a hydrophilic functional group does not contain calcium carbonate and contains kaolin and / or illite as a filler. And a water-absorbing pigment and an aqueous binder provided on at least one side of the base paper as main components, and a solid content of 0.5 to 3.0 g / m ² per side Inkjet recording paper comprising a recording layer has been proposed.
However, Patent Documents 4 and 5 have a problem that ink water reaches the base paper and causes cockling and curling.

JP 2005-238829 A JP 2005-96285 A JP 2007-130791 A Japanese Patent Laid-Open No. 6-219044 JP-A-8-244337

  An object of the present invention is to solve the conventional problems and achieve the following objects. That is, the present invention provides a recording medium capable of performing high-quality printing equivalent to offset printing at low cost and at high speed, a method for producing the recording medium, and an ink jet recording method using the recording medium. Objective.

Means for solving the problems are as follows. That is,
<1> In a recording medium in which a base paper, a first layer containing a binder, and a second layer containing a white pigment are sequentially laminated, the base paper provided with the first layer is defined in JIS P8140. Cobb water absorption degree during a contact time 15 seconds by water absorption test to be is at 5.0 g / m ² or less, and said second layer, water absorption 2 mL / m at a contact time of 0.5 sec determined by the Bristow method ^The recording medium is characterized by being ² or more and 8 mL / m ² or less.
<2> The recording according to <1>, wherein the base paper provided with the first layer has a Cobb water absorption of 2.0 g / m ² or less at a contact time of 2 minutes according to a water absorption test specified in JIS P8140. It is a medium.
<3> The base paper provided with the first layer has a Cobb value of a contact time of 2 minutes determined using diethylene glycol based on a water absorption test specified in JIS P8140 of 5.0 g / m ² or less. and, the second layer, the water absorption amount at a contact time of 0.9 seconds was determined is 1 mL / ^{m 2} or more 6 mL / ^{m 2} or less with pure water containing 30 wt% of diethylene glycol by Bristow's method < The recording medium according to any one of <1> to <2>.
<4> The recording medium according to any one of <1> to <3>, wherein a layer surface pH of the second layer is less than 8.0 before pH adjustment.
<5> The white pigment according to any one of <1> to <4>, wherein the white pigment includes only a white pigment having a pH of less than 8.0 according to a pH value test method (normal temperature extraction method) defined in JIS K5101. It is a recording medium.
<6> The white pigment has a pH of less than 6.0 after adding 0.1 mL of 1 mol / L hydrochloric acid to 10 g of a measurement solution of the pH value test method (normal temperature extraction method) defined in JIS K5101. The recording medium according to any one of <1> to <5>.
<7> The recording medium according to any one of <1> to <6>, wherein the layer surface pH of the second layer is 5.5 or less after pH adjustment.
<8> The recording medium according to any one of <1> to <7>, wherein the binder in the first layer includes a thermoplastic resin.
<9> The recording medium according to <8>, wherein the thermoplastic resin is at least one selected from polyester urethane latex and acrylic silicone latex.
<10> The recording medium according to any one of <1> to <9>, wherein the first layer further contains a layered inorganic compound.
<11> The recording medium according to any one of <1> to <10>, wherein the first layer further contains a white pigment.
<12> The recording medium according to <11>, wherein the white pigment is kaolin.
<13> Kaolin is the recording medium according to <12>, wherein the aspect ratio is 30 or more.
<14> From the above <1> to <13>, including a first forming step of forming a first layer on the base paper and a second forming step of forming a second layer on the first layer. The method for producing a recording medium according to any one of the above, wherein in the first forming step, the thermoplastic resin fine particles provided on the surface of the base paper are placed in a temperature range equal to or higher than the minimum film forming temperature of the thermoplastic resin fine particles. A method for manufacturing a recording medium, characterized by performing heat treatment.
<15> The coating liquid for forming the second layer has a shear rate D (= S / (t) defined by the coating speed S (m / min) and the film thickness t (μm) of the coating layer. X60 × 10 ⁻⁶ )) is in the range of 10 ^{3 to} 10 ⁶ (s ⁻¹ ), and the high shear viscosity is 20 mPa · s to 150 mPa · s. It is a manufacturing method.
<16> The method for producing a recording medium according to any one of <14> to <15>, wherein in the second forming step, a coating liquid for forming the second layer is applied by a blade coating method. It is.
<17> An ink drawing process for drawing ink according to predetermined image data on the recording medium according to any one of <1> to <13>, and drying an ink solvent in the ink drawn recording medium And a dry removal step of removing the ink jet recording method.
<18> A treatment liquid supply step of supplying a treatment liquid containing an acidic substance to the recording medium according to any one of <1> to <13>, and a predetermined amount with respect to the recording medium supplied with the treatment liquid An ink jet recording method comprising: an ink drawing step of drawing ink in accordance with image data; and a drying removal step of drying and removing an ink solvent in the ink drawn recording medium.

  According to the present invention, it is possible to solve the above-described conventional problems, achieve the above-described object, and perform a high-quality printing equivalent to the offset printing at a low cost and at a high speed. A manufacturing method and an ink jet recording method using the recording medium can be provided.

  Hereinafter, a recording medium of the present invention, a method for producing the recording medium, and an ink jet recording method using the recording medium will be described with reference to the drawings.

(recoding media)
The recording medium of the present invention includes a base paper, a first layer, and a second layer, and further includes other layers appropriately selected as necessary.
For example, as shown in FIG. 1, the recording medium 100 includes a high quality paper 11 as a base paper, a solvent blocking layer 12 as a first layer formed on the high quality paper 11, and a solvent blocking layer 12. And an ink absorption layer 13 as a formed second layer.
The recording medium may be either sheet paper or roll paper.

<Base paper>
There is no restriction | limiting in particular as said base paper, According to the objective, it can select suitably from well-known things.

  The pulp that can be used as the raw material of the base paper is preferably hardwood bleached kraft pulp (LBKP) from the viewpoint of improving the surface smoothness, rigidity and dimensional stability (curlability) of the base paper to a balanced and sufficient level. However, softwood bleached kraft pulp (NBKP), hardwood sulfite pulp (LBSP) and the like can also be used.

  A beater or refiner can be used for beating the pulp. The pulp slurry obtained after beating the pulp (hereinafter sometimes referred to as “pulp stock”) includes various additives as necessary, for example, filler, dry paper strength enhancer, sizing agent, and wet. A paper strength enhancer, a fixing agent, a pH adjuster, other chemicals, and the like are added.

  Examples of the filler include calcium carbonate, clay, kaolin, white clay, talc, titanium oxide, diatomaceous earth, barium sulfate, aluminum hydroxide, magnesium hydroxide and the like. Examples of the dry paper strength enhancer include cationized starch, cationized polyacrylamide, anionized polyacrylamide, amphoteric polyacrylamide, and carboxy-modified polyvinyl alcohol. Examples of the sizing agent include rosin derivatives such as fatty acid salts, rosin and maleated rosin, paraffin wax, alkyl ketene dimer, alkenyl succinic anhydride (ASA), and epoxidized fatty acid amide.

  Examples of the wet paper strength enhancer include polyamine polyamide epichlorohydrin, melamine resin, urea resin, and epoxidized polyamide resin. Examples of the fixing agent include polyvalent metal salts such as aluminum sulfate and aluminum chloride, and cationic polymers such as cationized starch. Examples of the pH adjuster include caustic soda and sodium carbonate.

  Examples of other chemicals include antifoaming agents, dyes, slime control agents, fluorescent whitening agents, and the like. Moreover, a softening agent etc. can also be added as needed. The softening agent is described in, for example, New Paper Processing Handbook (edited by Paper Medicine Time), pages 554 to 555 (issued in 1980).

  The treatment liquid used for the surface sizing treatment may contain, for example, a water-soluble polymer, a sizing agent, a water-resistant substance, a pigment, a pH adjusting agent, a dye, and a fluorescent brightening agent. Examples of the water-soluble polymer include cationized starch, polyvinyl alcohol, carboxy-modified polyvinyl alcohol, carboxymethyl cellulose, hydroxyethyl cellulose, cellulose sulfate, gelatin, casein, sodium polyacrylate, styrene-maleic anhydride copolymer sodium salt, Examples thereof include sodium polystyrene sulfonate.

  Examples of the sizing agent include petroleum resin emulsion, ammonium salt of styrene-maleic anhydride copolymer alkyl ester, rosin, higher fatty acid salt, alkyl ketene dimer (AKD), epoxidized fatty acid amide and the like.

  Examples of the water resistant substance include latex / emulsions such as styrene-butadiene copolymer, ethylene-vinyl acetate copolymer, polyethylene, vinylidene chloride copolymer, and polyamide polyamine epichlorohydrin.

  Examples of the pigment include calcium carbonate, clay, kaolin, talc, barium sulfate, and titanium oxide. Examples of the pH adjuster include hydrochloric acid, caustic soda, sodium carbonate, and the like.

  Examples of the material of the base paper include synthetic pulp paper, mixed paper of natural pulp and synthetic pulp, and various types of combined paper, in addition to the above-described natural pulp paper. The base paper is 30 to 500 μm, preferably 50 to 300 μm, more preferably 70 to 200 μm.

<First layer>
The first layer contains a binder and has a Cobb water absorption of 5.0 g / m ² or less at a contact time of 15 seconds according to a water absorption test specified in JIS P8140 on the base paper provided with the first layer. As long as it is, it is not particularly limited and can be appropriately selected from known ones according to the purpose. For example, according to the water absorption test defined in JIS P8140 on the base paper provided with the first layer. Cobb water absorption at a contact time of 2 minutes was 2.0 g / m ² or less, and was determined using diethylene glycol based on the water absorption test defined in JIS P8140 on the base paper provided with the first layer. it Cobb value of the contact time of 2 minutes is 5.0 g / ^{m 2} or less, as a binder, a thermoplastic resin and polyvinyl alcohol (in particular, the degree of polymerization 1000 or more Of acetoacetyl-modified polyvinyl alcohol), further containing a layered inorganic compound, mass ratio X of mass X of polyvinyl alcohol and mass Y of water-swellable synthetic mica as the layered inorganic compound / Y is preferably 1 or more and 30 or less, further containing a hardening agent, further containing a white pigment, and the like.

A base paper provided with a solvent blocking layer (first layer) has a paper strength of 5 g / m ² when the Cobb water absorption is 15 g / m ² or less according to the water absorption test specified in JIS P 8140. It is possible to prevent deformation due to lowering and swelling. Preferably, the Cobb water absorption at a contact time of 2 minutes according to the water absorption test specified in JIS P 8140 is 2.0 g / m ² or less, and diethylene glycol based on JIS P 8140. If the Cobb value with a contact time of 2 minutes using is 5.0 g / m ² or less, the paper strength can be reduced and deformation due to swelling can hardly occur.

As a specific means, a water-dispersible latex in which a hydrophobic polymer insoluble or hardly soluble in water is dispersed as fine particles in an aqueous phase dispersion medium as a main component, the solid content is 3 to 20 g / m ² per side. By coating, almost complete water resistance is obtained.

  Further, in order to give the resin surface hydrophilicity that does not repel water, by preparing a solvent blocking layer in which white pigment is blended in an amount of 5 to 50 parts by weight per 100 parts of the binder, Application by laminating two layers becomes easy, and a base paper provided with a first layer compatible with water resistance is obtained.

  A white pigment having an aspect ratio of 30 or more can be blended up to 200 parts by weight of the white pigment per 100 parts by weight of the above-mentioned binder. It becomes good.

<< Binder >>
The binder contained in the first layer is not particularly limited as long as it contains at least one of a thermoplastic resin and polyvinyl alcohol, but preferably contains a thermoplastic resin.

<< Thermoplastic resin >>
There is no restriction | limiting in particular as a thermoplastic resin, It uses selecting suitably from well-known thermoplastic resins and its latex, such as polyolefin resin (For example, the homopolymer of α-olefins, such as polyethylene and a polypropylene, or a mixture thereof). Can do. Among these, latex is preferable, polyester urethane latex, acrylic latex, acrylic silicone latex, acrylic epoxy latex, acrylic styrene latex, acrylic urethane latex, styrene-butadiene latex, acrylonitrile-butadiene latex, and vinyl acetate. Preferred are latexes, and it is preferable to use at least one selected from these. Among these, it is particularly preferable to select and use at least one selected from polyester urethane latex and acrylic silicone latex.

Examples of the polyester urethane latex include Hydran AP series and Hydran ECOS series manufactured by Dainippon Ink & Chemicals, Inc.
As the acrylic latex, a commercially available product can be used. For example, the following water-dispersible latex can be used. That is, examples of acrylic resins include “Cebian A4635, 46583, 4601” manufactured by Daicel Chemical Industries, Ltd., “Nipol Lx811, 814, 821, 820, 857” manufactured by Nippon Zeon Co., Ltd. .
In particular, acrylic emulsions of acrylic silicone latex described in JP-A-10-264511, JP-A-2000-43409, JP-A-2000-343811, and JP-A-2002-120452 (commercially available products include, for example, Daicel Trade names “Aquabrid Series UM7760, UM7611, UM4901, MSi-045, ASi-753, ASi-903, ASi-89, ASi-91, ASi-86, 4635, MSi-04S, AU manufactured by Chemical Industry Co., Ltd. -124, AU-131, AEA-61, AEC-69, AEC-162 ") and the like can also be suitably used.
In addition, said thermoplastic resin can also use 2 or more types together not only individually by 1 type.

  The glass transition temperature (Tg) of the thermoplastic resin is preferably 5 to 70 ° C, and particularly preferably 15 to 50 ° C. By making the Tg particularly in the above range, there is no difficulty in handling such as causing problems such as burrs of the first layer forming liquid (for example, coating liquid), and the Tg is too high. If the calendar temperature is not set to a very high level, the desired gloss cannot be obtained, and adhesion to the metal roll surface is likely to occur. High flatness can be obtained.

  Moreover, as minimum film-forming temperature of a thermoplastic resin, 20-60 degreeC is preferable and 25-50 degreeC is more preferable. By making the minimum film forming temperature range where film formation is possible when trying to form a film within the above range, problems such as burrs of the liquid for forming the first layer (for example, coating liquid) may occur. Sufficiently small pores to pass through the ink solvent quickly without being difficult to handle and without causing significant penetration when the second layer is formed and reducing the surface of the layer. It can be comprised in the layer which has property. Although a layer only provided with a liquid (for example, a coating liquid) does not have good glossiness, a high glossiness layer having microporosity can be obtained by performing a soft calender treatment later.

  In the case where the composition is formed in layers, the content of the thermoplastic resin in the first layer is preferably 15 to 95% by mass, and preferably 30 to 90% by mass with respect to the solid content of the first layer. % Is more preferable. By making the content particularly within the above range, ink solvent permeability can be obtained without impairing glossiness and flatness after calendar treatment, and the occurrence of bleeding over time can be more effectively prevented. Can do.

<< Polyvinyl alcohol >>
In addition to polyvinyl alcohol (PVA), polyvinyl alcohol includes cation-modified polyvinyl alcohol, anion-modified polyvinyl alcohol, silanol-modified polyvinyl alcohol, acetoacetyl-modified polyvinyl alcohol, and other polyvinyl alcohol derivatives. Polyvinyl alcohol can be used alone or in combination of two or more. Among these, polyvinyl alcohol and acetoacetyl-modified polyvinyl alcohol can be preferably used.

  The polyvinyl alcohol in the present invention preferably has a saponification degree of 70 to 99%, more preferably 85 to 99% mono. Moreover, as a polymerization degree, the thing of 1000-4500 is preferable, and the thing of 1500-4500 is more preferable. By setting the saponification degree and the polymerization degree within the above ranges, sufficient film strength and extensibility can be obtained.

<< acetoacetyl-modified polyvinyl alcohol >>
In general, acetoacetyl-modified polyvinyl alcohol can be produced by adding and reacting a liquid or gaseous diketene to a solution, dispersion or powder of a polyvinyl alcohol resin. The degree of acetylation of the acetoacetyl-modified polyvinyl alcohol can be appropriately selected according to the quality of the target heat-sensitive recording material, but is 0.1 mol% to 20 mol%, more preferably 0.5 mol% to 10 mol%.

  The polyvinyl alcohol resin is obtained by saponifying a polyvinyl alcohol obtained by saponifying a lower alcohol solution of polyvinyl acetate and a derivative thereof, and a copolymer of a monomer capable of copolymerizing with vinyl acetate and vinyl acetate. included. Here, as monomers that can be copolymerized with vinyl acetate, (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid, (meth) acrylic acid and other unsaturated carboxylic acids and esters thereof, ethylene, propylene, etc. Α-olefin, olefin sulfonic acid such as (meth) allyl sulfonic acid, ethylene sulfonic acid, sulfonic acid malate, (meth) allyl sulfonic acid soda, ethylene sulfonic acid soda, sulfonic acid soda (meth) acrylate, sulfonic acid soda ( Monoalkyl malate), olefin sulfonic acid alkali salts such as sodium disulfonic acid alkyl malate, amide group-containing monomers such as N-methylol acrylamide, acrylamide alkyl sulfonic acid alkali salts, and N-vinyl pyrrolidone derivatives. Can be mentioned.

As the binder, in addition to the above-mentioned acetyl-modified polyvinyl alcohol, if necessary, a compound that dissolves 5% by mass or more in water at 25 ° C. may be used in combination. As these binders, polyvinyl alcohol (including modified polyvinyl alcohols such as carboxy-modified, itaconic acid-modified, maleic acid-modified, silica-modified and amino group-modified), methylcellulose, carboxymethylcellulose, starches (including modified starch), gelatin Arabic rubber, casein, styrene-maleic anhydride copolymer hydrolyzate, polyacrylamide, saponified vinyl acetate-polyacrylic acid copolymer, and the like. These binders are used not only for dispersion but also for the purpose of improving the film strength. For this purpose, styrene / butadiene copolymer, vinyl acetate copolymer, acrylonitrile / butadiene copolymer, acrylic acid are used. Synthetic polymer latex binders such as methyl-butadiene copolymer and polyvinylidene chloride can be used in combination. Moreover, according to the kind of these binders, you may add the crosslinking agent of a suitable binder as needed.
Moreover, the acetoacetyl modified polyvinyl alcohol contained in the first layer has large oxygen permeation suppression and high SS characteristics. Here, the SS characteristic means a tensile energy absorption amount (toughness) expressed by stress-elongation until the film breaks. Therefore, the first layer freely expands and contracts even in a process that requires heating, does not generate a crack, and does not easily generate blisters.

  In the present invention, the degree of polymerization of acetoacetyl-modified polyvinyl alcohol is preferably 1,000 or more, and more preferably 1,500 or more. When the degree of polymerization is 1,000 or more, the effect of suppressing the occurrence of cracks in a low humidity environment (for example, 20 ° C., 10% RH) is increased. This is considered due to the fact that the strength and elongation at break can be remarkably increased by increasing the degree of polymerization to 1,000 or more. Further, when the degree of polymerization is increased, the viscosity of the coating liquid is improved and the surface state of the coating is lowered. However, the disadvantage can be compensated by reducing the concentration of the coating liquid and the ratio of the water-dispersible mica.

  The modification rate of the acetoacetyl-modified polyvinyl alcohol is preferably 0.05 to 20 mol% from the viewpoint of water resistance by reaction with a hardener and stability in an aqueous solution. More preferably, it is mol%.

  The saponification degree of the acetoacetyl-modified polyvinyl alcohol is not particularly limited, but is preferably 80 to 99.5%. If the degree of saponification decreases, the elongation at break increases. Further, when the degree of polymerization is high, the degree of saponification increases, but when the degree of polymerization is low, it is preferable to reduce the degree of saponification. Further, when the degree of saponification is lowered, the elongation can be increased, while there are advantages that the viscosity is lowered and the leveling of the coated surface is improved and the coated surface is improved.

<< Cobb water absorption >>
The Cobb water absorbency is obtained by a water absorbency test specified in JIS P8140, and measures the amount of water absorbed when water contacts from one side of paper for a certain period of time. The contact time was 15 seconds and 2 minutes.

<< Cobb value >>
The Cobb value is a value obtained by measuring the amount of diethylene glycol absorbed when diethylene glycol contacts from one side of the paper for a certain period of time based on a water absorption test method defined in JIS P8140, with a contact time of 2 minutes. The contact time was 2 minutes.

<< Layered inorganic compound >>
The first layer preferably further contains a layered inorganic compound. As the layered inorganic compound, a swellable inorganic layered compound is preferable, and examples of these compounds include swellable viscosity minerals such as bentonite, hectorite, saponite, beiderite, nontronite, stevensite, beidellite, montmorite, and swelling. Synthetic mica, swellable synthetic smectite, and the like. These swellable inorganic layered compounds have a laminated structure composed of unit crystal lattice layers having a thickness of 1 to 1.5 nm, and the substitution of metal atoms in the lattice is significantly larger than other clay minerals. As a result, the lattice layer is deficient in positive charge, and cations such as Na ⁺ , Ca ²⁺ and Mg ²⁺ are adsorbed between the layers in order to compensate for this. The cations present between these layers are called exchangeable cations and exchange with various cations. In particular, when the cation between layers is Li ⁺ , Na ⁺ or the like, since the ionic radius is small, the bond between the layered crystal lattices is weak, and the layer swells greatly with water. If shear is applied in this state, it will be easily cleaved to form a stable sol in water. Bentonite and swellable synthetic mica have a strong tendency and are preferable for the purpose of the present invention. In particular, water-swellable synthetic mica is preferable.

Examples of water-swellable synthetic mica include Na tetrathic mica NaMg _2.5 (Si ₄ O ₁₀ ) F ₂ Na, Li teniolite (NaLi) Mg ₂ (Si ₄ O ₁₀ ) F ₂ Na, or Li hectorite (NaLi). / 3Mg ₂ / 3Li _1/3 Si ₄ O ₁₀ ) F _{2 and the} like.

  The water-swellable synthetic mica preferably used in the present invention has a thickness of 1 to 50 nm and a surface size of 1 to 20 μm. For diffusion control, the thinner the better, the better the plane size, as long as the smoothness and transparency of the coated surface are not deteriorated. Accordingly, the aspect ratio is 100 or more, preferably 200 or more, particularly preferably 500 or more.

<< mass ratio >>
The mass ratio X / Y of the mass X of the acetoacetyl-modified polyvinyl alcohol and the mass Y of the water-swellable synthetic mica contained in the first layer is preferably in the range of 1 to 30, and preferably 5 to 15. The following range is more preferable. When the mass ratio is in the range of 1 or more and 30 or less, the effect is great in suppressing oxygen permeation and blistering.

<< Hardener >>
The hardening agent in the first layer of the present invention includes an aldehyde compound, 2,3-dihydroxy-1,4-dioxane and derivatives thereof, and a vinyl adjacent to a substituent having a positive Hammett substituent constant σp. It is at least one selected from compounds having two or more groups in a single molecule. The first layer in the present invention is adjacent to a aldehyde compound, 2,3-dihydroxy-1,4-dioxane and a derivative thereof, and a substituent having a positive Hammett's substituent constant σp as a hardener. By containing at least one selected from compounds having two or more vinyl groups in a single molecule, it reacts with acetoacetyl-modified polyvinyl alcohol without increasing the viscosity of the first layer coating solution Thus, the water resistance of the recording material can be improved, and as a result, a recording material in which the water resistance of the recording material and the coating stability of the first layer coating solution are improved can be obtained.

As substituents having a positive Hammett's substituent constant σp, CF ₃ group (σp value: 0.54), CN group (σp value: 0.66), COCH ₃ group (σp value: 0.50), COOH group (σp value: 0.45), COOR (R represents an alkyl group) group (σp value: 0.45), NO ₂ group (σp value: 0.78), OCOCH ₃ group (σp value: 0.31), SH group (σp value: 0.15), SOCH ₃ group (σp value: 0.49), SO ₂ CH ₃ group (σp value: 0.72), SO ₂ NH ₂ group (σp value) : 0.57), SCOCH ₃ group (σp value: 0.44), F group (σp value: 0.06), Cl group (σp value: 0.23), Br group (σp value: 0.23) , I group (σp value: 0.18), IO ₂ group (σp value: 0.76), N ⁺ (CH ₃ ) ₂ group (σp value: 0.82), S ⁺ (CH ₃ ) ₂ group ( σp value: 0. 0), and the like.

  The compound having two or more vinyl groups adjacent to a substituent having a positive Hammett substituent constant σp in a single molecule is 2-ethylenesulfonyl-N- [2- (2-ethylenesulfonyl-acetylamino). ) -Ethyl] acetamide, bis-2-vinylsulfonylethyl ether, bisacryloylimide, NN′-diaacryloylurea, 1,1-bisvinylsulfoneethane, ethylene-bis-acrylamide, and the following structural formula And 2-ethylenesulfonyl-N- [2- (2-ethylenesulfonyl-acetylamino) -ethyl] acetamide is particularly preferable among them.

  The content of the compound having two or more vinyl groups adjacent to the substituent having a positive Hammett's substituent constant σp in the first layer in the single molecule is 0. 1 mass% or more and 30 mass% or less are preferable, and 0.5 mass% or more and 10 mass% or less are more preferable. When the content of the compound in the first layer is 0.5% by mass or more and 10% by mass or less with respect to acetoacetyl-modified polyvinyl alcohol, the first layer coating liquid does not thicken. Further, the effect of the above-described compound in the present invention that the water resistance of the recording material can be improved can be further exhibited.

<< white pigment >>
Examples of the white pigment include titanium oxide, barium sulfate, barium carbonate, calcium carbonate, lithopone, alumina white, zinc oxide, silica, antimony trioxide, titanium phosphate, aluminum hydroxide, kaolin, clay, talc, magnesium oxide, And magnesium hydroxide. These can be used individually by 1 type or in mixture of 2 or more types. Of these, kaolin is particularly preferred.

<<<< Kaolin >>>>
The kaolin preferably has an aspect ratio (diameter / thickness) of 30 or more. Examples of kaolin having an aspect ratio of 30 or higher include engineered grades (for example, Contour 1500 (aspect ratio 59), Astra-Plate (aspect ratio 34)). Further, when the kaolin has a high whiteness and a steep particle size distribution (uniform particle size), it provides excellent whiteness and printing suitability for various coated papers.

  The particle size of the white pigment is preferably 75% or more of particles of 2 μm or less, and more preferably 0.1 to 0.5 μm in average particle size. By setting the particle size in the above range, it is possible to effectively avoid a decrease in whiteness or a decrease in gloss.

  The titanium oxide may be either a rutile type or an anatase type, and these may be used alone or in combination. Further, any of those manufactured by the sulfuric acid method and those manufactured by the chlorine method may be used. Examples of the titanium oxide include hydrous alumina treatment, hydrous silicon dioxide treatment, or surface coating treatment with an inorganic substance such as zinc oxide treatment, trimethylolmethane, trimethylolethane, trimethylolpropane, and 2,4-dihydroxy-2. -It can select suitably from what carried out surface coating processing by organic substances, such as methylpentane, or siloxane processing, such as polydimethylsiloxane.

  The refractive index of the white pigment is preferably 1.5 or more. When a white pigment having a refractive index in this range is included, a high-quality image can be formed.

Further, the specific surface area of the white pigment by the BET method is preferably less than 100 m ² / g, and when a white pigment having a specific surface area in this range is included, the coating liquid for coating and forming the second layer Infiltration can be suppressed and the ink absorbability of the second layer can be increased.
The BET method is a method for measuring the surface area of a powder by a gas phase adsorption method, and is a method for determining the total surface area, that is, the specific surface area of a 1 g sample from an adsorption isotherm. Usually, nitrogen gas is used as the adsorbed gas, and a method of measuring the amount of adsorption from the change in pressure or volume of the gas to be adsorbed is common. A prominent expression of the isotherm of multimolecular adsorption is the Brunauer Emmett and Teller equation (BET equation). Based on this, the amount of adsorption is obtained, and the surface area is obtained by multiplying the area occupied by one adsorbed molecule. .

In the case where the composition is formed in layers, the content of the white pigment in the first layer varies depending on the type of white pigment, the type of thermoplastic resin, the layer thickness, etc. Usually, about 50 parts by mass to 200 parts by mass is preferable with respect to parts.
In addition, well-known additives, such as antioxidant, can also be added to a 1st layer.

  As a film thickness at the time of forming a 1st layer using the said composition, the range of 1-30 micrometers is preferable, and the range of 5-20 micrometers is more preferable. By making the film thickness within the above range, it is possible to obtain the glossiness of the surface that has been calendered later and the whiteness with a small amount of white pigment, and at the same time, the handleability such as the bendability is equivalent to that of coated paper and art paper. Can be. In addition, since the first layer contains a white pigment, there is an effect that sticking to the calendar can be prevented when the calendar treatment is performed after the first layer is applied.

<Second layer>
The second layer contains a white pigment and is not particularly limited as long as the water absorption amount at a contact time of 0.5 seconds by the Bristow method is 2 mL / m ² or more and 8 mL / m ² or less. For example, the water absorption amount for a contact time of 0.9 seconds obtained using pure water containing 30% by mass of diethylene glycol by the Bristow method is 1 mL / m ² or more and 6 mL / m ^2. It is below, it contains further other binders (thermoplastic resin), it contains 10-60 parts of solid resin per 100 parts of solid part of white pigment, and the layer surface pH is acidic. Etc. are preferred.

In the second layer, when the water absorption amount at a contact time of 0.5 seconds by the Bristow method exceeds 8 mL / m ² , the ink solvent is rapidly absorbed into the recording medium, and the ink aggregation reaction near the surface hardly occurs. The image is transferred to a fixing roller, and the printed matter becomes dirty.

Further, when the water absorption is less than 2 mL / m ² , a problem arises that the solvent is embraced during the ink agglomeration reaction and the image is deformed.

When the water absorption amount with a contact time of 0.9 seconds determined by using Bristow's method using pure water containing 30% by mass of diethylene glycol close to the actual ink solvent component exceeds 6 mL / m ² , the same printed matter stains as described above. If the water absorption amount is less than 1 mL / m ² , there arises a problem of image deformation.

The second layer has a water absorption amount of 2 mL / m ² or more and 8 mL / m ² or less, with a contact time of 0.5 seconds determined by the Bristow method, preferably determined using pure water containing 30% by mass of diethylene glycol by the Bristow method. As a specific means for adjusting the water absorption amount for 0.9 second contact time to 1 mL / m ² or more and 6 mL / m ² or less, in the second layer, the blending range of the binder per 100 parts by mass of the white pigment is set. 5 to 15 parts by mass.

<< white pigment >>
The white pigment is not particularly limited. For example, calcium carbonate, kaolin, titanium dioxide, aluminum trihydroxide, zinc oxide, barium sulfate, satin white, talc and the like are generally used as white pigments for coated paper for printing. You can choose from the inside. By including the white pigment in the second layer, there is an effect that the pigment in the ink can be retained in the second layer.
The white pigment is preferably composed only of a white pigment having a pH of less than 8.0 (preferably 7.5 or less) according to a pH value test method (normal temperature extraction method) defined in JIS K5101. When the pH exceeds 8.0, the surface pH of the second layer becomes high, and a general coloring material in the ink has an anionic charge (anionic dissociation group), so that the coloring material is dissolved. In addition, the dispersion is relatively stable, the color material is less likely to agglomerate, and image deterioration may occur due to image blurring and deformation of the droplet after landing.
The white pigment has a pH of less than 6.0 after adding 0.1 mL of 1 mol / L hydrochloric acid to 10 g of a measurement solution of the pH value test method (normal temperature extraction method) defined in JIS K5101. Is preferably 5.0 or less, more preferably 4.0 or less. When the pH is 6.0 or more, the surface pH of the second layer becomes high, which may cause image bleeding and image quality deterioration. In addition, an acid or the like is used to promote aggregation of the coloring material. When the pH of the second layer is adjusted to be low, the white pigment is neutralized to increase the surface pH, thereby reducing the effect of pH adjustment and causing image bleeding and image quality deterioration. Sometimes.
Examples of such pigments include kaolin, titanium oxide, and a mixture of kaolin and titanium oxide.
The content of the white pigment in the second layer is preferably 50% by mass to 98% by mass, and more preferably 70% by mass to 97% by mass.

<< Bristow method >>
The Bristow method is the most popular method for measuring the amount of liquid absorbed in a short time, and is also adopted by the Japan Paper Pulp Technology Association (J'TAPPI). Details of the test method are described in J'TAPPI No. 51, “Method for testing liquid absorbency of paper and paperboard”. At the time of measurement, the head box slit width of the Bristow test is adjusted according to the surface tension of the ink. Also, the point where the ink is removed from the back of the paper is excluded from the calculation.

<< Binder (thermoplastic resin) >>
There is no restriction | limiting in particular as a binder (thermoplastic resin), For example, the thing similar to what was used by the 1st layer can be used. The content of the binder in the second layer is preferably 2 parts by mass to 50 parts by mass with respect to 100 parts by mass of the white pigment, and more preferably 3 parts by mass to 30 parts by mass.

<< layer surface pH >>
By adjusting the surface pH of the second layer to be acidic, the ink can be aggregated and the fixing of the ink can be improved.
The layer surface pH of the second layer is preferably less than 8.0 before pH adjustment, and more preferably 7.5 or less. If the layer surface pH before pH adjustment is 8.0 or more, the image may be blurred and the image quality may be lowered. Also, the second layer may be formed using an acid or the like to promote the aggregation of the coloring material. When the pH is adjusted to be low, the white pigment is neutralized to increase the surface pH, thereby reducing the effect of pH adjustment and causing image bleeding and image quality deterioration.
In addition, the layer surface pH of the second layer is preferably 5.5 or less, more preferably 4.5 or less after pH adjustment. If the pH of the layer surface after the pH adjustment exceeds 5.5, the image may be blurred or the image quality may be deteriorated.
Here, the measurement of the surface pH can be performed by the A method (coating method) in the measurement of the film surface PH defined by the Japan Paper Pulp Technology Association (J.TAPPI), and corresponds to, for example, the A method. It can be performed using a PH measurement set for paper “model MPC” manufactured by Kyoritsu Riken Co., Ltd.

  The pH adjustment may be performed by adding an acid to the surface of the recording medium, although it may be added to the coating solution on the surface of the second layer or an acid may be applied to the surface of the recording medium. Specifically, it is preferable to carry out by applying a treatment liquid containing an acidic substance. As the acidic substance, for example, a phosphoric acid group, a phosphonic group, a phosphine group, a sulfuric acid group, a sulfonic acid group, a sulfinic acid, a carboxylic acid or a salt thereof can be used, and a phosphoric acid group, a sulfonic acid group, a carboxylic acid group can be used. It is more preferable that Examples of phosphoric acid include phosphoric acid, polyphosphoric acid, metaphosphoric acid, or derivatives of these compounds, or salts thereof. Examples of sulfonic acid include methanesulfonic acid, polysulfonic acid, or derivatives of these compounds, or salts thereof. As carboxylic acids, oxalic acid, tartaric acid, malic acid, malonic acid, citric acid, fumaric acid, maleic acid, succinic acid, salicylic acid, phthalic acid, lactic acid, acetic acid, trichloroacetic acid, chloroacetic acid, polyacrylic acid, Or derivatives of these compounds, or salts thereof, and compounds having furan, pyrrole, pyrroline, pyrrolidone, pyrone, pyrrole, thiophene, indole, pyridine, quinoline structure, and further having a carboxyl group as a functional group, etc. For example, pyrrolidone carboxylic acid, pyrone carboxylic acid, pyrrole cal Phosphate, furan carboxylic acid, pyridine carboxylic acid, cumaric acid, thiophene carboxylic acid, nicotinic acid, or derivatives of these compounds, or salts thereof. In addition, acids such as hydrochloric acid, sulfuric acid and nitric acid can be used.

<Other layers>
There is no restriction | limiting in particular as another layer, According to the objective, it can select suitably.

(Recording medium manufacturing method)
The method for producing a recording medium of the present invention includes a first forming step and a second forming step, and further includes other steps appropriately selected as necessary.

<First forming step>
In the first forming step, the first layer is formed on the base paper, and in the first forming step, the thermoplastic resin fine particles provided on the surface of the base paper are used as the minimum film-forming temperature of the thermoplastic resin fine particles. There is no restriction | limiting in particular except heat-processing in the above temperature range, According to the objective, it can select suitably. Note that pressure may be applied in the heat treatment.

  There is no restriction | limiting in particular as said thermoplastic resin particle, All the particles of a conventionally well-known thermoplastic resin are included. Examples of such known thermoplastic resins include general-purpose thermoplastic polymers such as polyolefins such as polyethylene, polypropylene and polyvinyl chloride; polyamides and polyimides; polyesters such as polyethylene terephthalate; Α-methylene aliphatic monocarboxylic acid esters such as methyl acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, dodecyl (meth) acrylate, octyl (meth) acrylate and phenyl (meth) acrylate Styrenes such as styrene, chlorostyrene and vinyl styrene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate; vinyl ethers such as vinyl methyl ether, vinyl ethyl ether and vinyl butyl ether; vinyl methyl ketone , Vini Hexyl ketone, homopolymer consisting of vinyl ketones such as vinyl isopropenyl ketone, or any copolymers including these structural units, and the like.

  The said thermoplastic resin particle may be used individually by 1 type, and may use 2 or more types together.

The thermoplastic resin particles preferably have an average particle size of 10 to 200 nm. Here, the value measured by the dynamic light scattering method (apparatus name: Otsuka Electronics Co., Ltd. ELS-800) is employ | adopted for the average particle diameter of the resin particle. Moreover, as a thermoplastic resin which comprises resin fine particles, the thing whose minimum film forming temperature (MFT) is 5-60 degreeC is preferable.
The coating amount of the thermoplastic resin is preferably ¹ to 30 g / m ² .

The thermoplastic resin particles preferably include water-dispersible latex-dispersed particles from the viewpoints of suppressing cockling, improving aging blur and suitability for production.
The water-dispersible latex is obtained by dispersing a hydrophobic polymer insoluble or hardly soluble in water as fine particles in an aqueous phase dispersion medium. As the dispersion state, the polymer is emulsified in a dispersion medium, emulsion-polymerized, micelle-dispersed, or partly hydrophilic in the polymer molecule and the molecular chain itself is molecularly dispersed. Any of these may be used. For such polymer latexes, edited by Taira Okuda and Hiroshi Inagaki “Synthetic Resin Emulsion” (published by Kobunshi Publishing Co., Ltd., 1978), Takaaki Sugimura, Ikuo Kataoka, Junichi Suzuki and Keiji Kasahara “Application of Synthetic Latex” ( Published by Kobunshi Shuppankai, 1993) and Soichi Muroi, “Chemistry of Synthetic Latex” (published by Kobunshi Shuppankai, 1970).

  Specific examples of the water-dispersible latex include acrylic latex, acrylic silicone latex, acrylic epoxy latex, acrylic styrene latex, acrylic urethane latex, styrene-butadiene latex, acrylonitrile-butadiene latex, and Preferable examples include at least one selected from vinyl acetate latexes.

The molecular weight of the water-dispersible latex is preferably 3,000 to 100,000 in terms of number average molecular weight, and more preferably about 5,000 to 100,000. If the molecular weight is too small, the mechanical strength of the undercoat forming layer may be insufficient, and if it is too large, it may be disadvantageous in terms of production suitability such as dispersion stability and viscosity.
Among the water-dispersible latexes, the first layer of the present invention is an acrylic silicone latex and an acrylic styrene latex from the viewpoint that the ink solvent permeability and cockling-inhibiting effect is high and the economy and manufacturing suitability can be combined. At least one selected from the above is most preferable.

<Second forming step>
There is no restriction | limiting in particular as a 2nd formation process except forming a 2nd layer on a 1st layer, Although it can select suitably according to the objective, A 2nd layer is formed. For the coating liquid for this, the shear rate D (= S / (t × 60 × 10 ⁻⁶ )) defined by the coating rate S (m / min) and the film thickness t (μm) of the coating layer is 10 ^{When the} viscosity is in the range of ³ or more and 10 ⁶ or less (s ⁻¹ ), the high shear viscosity is 20 mPa · s or more and 150 mPa · s or less, and the coating liquid for forming the second layer depends on the blade coating method. It is preferably applied.

<< High shear viscosity >>
The high shear viscosity of the coating solution for the topcoat layer (second layer) is preferably 30 mPa · s to 150 mPa · s, more preferably 40 mPa · s to 140 mPa · s.
When the high shear viscosity is less than 20 mPa · s, the coating amount for the topcoat layer does not penetrate into the undercoat layer, unlike the direct coating on the base paper, so the coating amount cannot be increased by blade coating. If it exceeds 150 mPa · s, the fluidity of the coating liquid for topcoat layer is impaired, making it unsuitable for handling.

<< Blade coating method >>
The blade coating method is a coating method in which a relatively large shear stress is generated at the moment of scraping the paint applied on the paper support.

<Other processes>
There is no restriction | limiting in particular as another process, According to the objective, it can select suitably.

(Inkjet recording method)
The ink jet recording method of the present invention includes an ink drawing process and a drying and removing process, and further includes other processes appropriately selected as necessary.

<Ink drawing process>
There is no restriction | limiting in particular as said ink drawing process other than drawing ink according to predetermined | prescribed image data, According to the objective, it can select suitably.

<Dry removal process>
The drying and removing step is not particularly limited except that the ink solvent in the recording medium on which the ink has been drawn is removed by drying, and can be appropriately selected according to the purpose. In the recording medium of the present invention, since the ink absorbing layer as the second layer is slowly permeable, the drying removal step is performed in a state where the ink solvent (water) is present near the surface of the recording medium.

<Other processes>
Other steps are not particularly limited and may be appropriately selected depending on the purpose. Examples thereof include a treatment liquid supply step and a heat fixing step.

-Processing liquid supply process-
There is no restriction | limiting in particular as said process liquid supply process except supplying the process liquid containing the acidic substance mentioned later, According to the objective, it can select suitably.

-Heat fixing process-
The heat fixing step is not particularly limited except that the latex particles contained in the ink used in the ink jet recording method are melt-fixed, and can be appropriately selected depending on the purpose.

  In the ink jet recording method, an ink jet recording method 1 (FIG. 2) that performs ink drawing or the like on a recording medium in which the second layer (ink absorbing layer) contains an ink and an aggregating agent (treatment liquid) in advance. And an ink jet recording method 2 (FIG. 3) in which ink drawing or the like is performed after supplying the processing liquid to the recording medium (pre-coating).

-Inkjet recording method 1
In the inkjet recording method 1, for example, ink drawing, drying (water drying, blow drying), and fixing are performed under the following conditions.

--Ink drawing--
Head: 1,200 dpi / 20 inch width full line head Discharged droplet amount: 4-value recording of 0, 2.0, 3.5, 4.0 pL Driving frequency: 30 kHz (recording medium conveyance speed 635 mm / sec)

-Drying (water drying, blow drying)-
Wind speed: 8-15m / s
Temperature: 40-80 ° C
Air blowing area: 640 mm (drying time 1 second)

--Fixing--
Silicone rubber roller (hardness 50 °, nip width 5mm)
Roller temperature: 70-90 ° C
Pressure: 0.5-2.0 MPa

-Inkjet recording method 2-
In the inkjet recording method 2, for example, pre-coating, ink drawing, drying (water drying, air drying), and fixing are performed under the following conditions.

--- Treatment liquid head for precoat module-
Head: 600 dpi / 20 inch width full line head Discharged droplet amount: binary recording of 0, 4.0 pL Drive frequency: 15 kHz (recording medium conveyance speed 635 mm / sec)
Drawing pattern: In the ink drawing process, a pattern that applies treatment liquid in advance to the position where at least one color ink is drawn is applied.

--- Water drying for precoat module (blow drying)-
Wind speed 8-15m / s, temperature 40-80 ° C, blowing area 450mm (drying time 0.7 seconds)

--Ink drawing--
Head: 1200 dpi / 20 inch full line head Discharged droplet amount: 4-value recording of 0, 2.0, 3.5, 4.0 pL Driving frequency: 30 kHz (recording medium conveyance speed 635 mm / sec)

-Drying (water drying, blow drying)-
Wind speed: 8-15m / s
Temperature: 40-80 ° C
Air blowing area: 640 mm (drying time 1 second)

--Fixing--
Silicone rubber roller (hardness 50 °, nip width 5mm)
Roller temperature: 70-90 ° C
Pressure: 0.5-2.0 MPa

<Water-based two-liquid aggregation ink>
In the ink jet recording method, an aqueous two-liquid aggregation ink comprising a treatment liquid and an ink that reacts and aggregates with the treatment liquid may be used.

-Treatment liquid-
As an acidic substance that makes the treatment solution acidic, a phosphoric acid group, a phosphonic acid group, a phosphinic acid group, a sulfuric acid group, a sulfonic acid group, a sulfinic acid, a carboxylic acid or a salt thereof can be used. It is more preferably an acid group, and further preferably a carboxylic acid group. Examples of the carboxylic acid include furan, pyrrole, pyrroline, pyrrolidone, pyrone, pyrrole, thiophene, indole, pyridine, a compound having a quinoline structure and a carboxyl group as a functional group, such as pyrrolidone carboxylic acid, pyrone carboxylic acid, Pyrrole carboxylic acid, furan carboxylic acid, pyridine carboxylic acid, coumaric acid, thiophene carboxylic acid, nicotinic acid, derivatives of these compounds, or salts thereof are added to the treatment liquid.

  Moreover, as said acidic substance, it is preferable that they are pyrrolidone carboxylic acid, pyrone carboxylic acid, furan carboxylic acid, coumaric acid, or these compound derivatives, or these salts. In addition, these compounds may be used by 1 type and may be used together 2 or more types.

  Further, the treatment liquid may contain other additives within a range that does not impair the effects of the present invention. Other additives include, for example, anti-drying agents (wetting agents), anti-fading agents, emulsion stabilizers, penetration enhancers, ultraviolet absorbers, preservatives, anti-fungal agents, pH adjusters, surface tension adjusters, Well-known additives, such as a foaming agent, a viscosity modifier, a dispersing agent, a dispersion stabilizer, a rust preventive agent, a chelating agent, are mentioned.

-Ink-
The ink can be used not only for forming a single color image but also for forming a full color image. In order to form a full color image, a magenta color ink, a cyan color ink, and a yellow color ink can be used, and a black color ink may be further used to adjust the color tone. Further, red, green, blue, and white inks other than yellow, magenta, and cyan color inks, and so-called special color inks (for example, colorless) in the printing field can be used. Examples of the ink include those containing latex particles, an organic pigment, a dispersant, and a water-soluble organic solvent, and further containing other additives as necessary.

--Latex particles--
Examples of the latex particles include a polymer of a compound composed of a nonionic monomer, an anionic monomer, and a cationic monomer.

  The nonionic monomer means a monomer compound having no dissociative functional group, and the monomer compound in a broad sense means a compound alone or a compound that polymerizes with another compound. The monomer compound is preferably a monomer compound having an unsaturated double bond.

  An anionic monomer represents a monomer compound containing an anionic group that can have a negative charge, and the anionic group may be any one as long as it has a negative charge. A phosphonic acid group, a phosphinic acid group, a sulfuric acid group, a sulfonic acid group, a sulfinic acid group or a carboxylic acid group, more preferably a phosphoric acid group or a carboxylic acid group, and a carboxylic acid group. Further preferred.

  The cationic monomer represents a monomer containing a cationic group that can have a positive charge, and any cationic group may be used as long as it has a positive charge. A substituent is preferable, and a cationic group of nitrogen or phosphorus is more preferable. Further, a pyridinium cation or an ammonium cation is more preferable.

--Organic pigments--
Examples of organic pigments for orange or yellow include C.I. I. Pigment orange 31, C.I. I. Pigment orange 43, C.I. I. Pigment yellow 12, C.I. I. Pigment yellow 13, C.I. I. Pigment yellow 14, C.I. I. Pigment yellow 15, C.I. I. Pigment yellow 17, C.I. I. Pigment yellow 74, C.I. I. Pigment yellow 93, C.I. I. Pigment yellow 94, C.I. I. Pigment yellow 128, C.I. I. Pigment yellow 138, C.I. I. Pigment yellow 151, C.I. I. Pigment yellow 155, C.I. I. Pigment yellow 180, C.I. I. And CI Pigment Yellow 185.

  Examples of organic pigments for magenta or red include C.I. I. Pigment red 2, C.I. I. Pigment red 3, C.I. I. Pigment red 5, C.I. I. Pigment red 6, C.I. I. Pigment red 7, C.I. I. Pigment red 15, C.I. I. Pigment red 16, C.I. I. Pigment red 48: 1, C.I. I. Pigment red 53: 1, C.I. I. Pigment red 57: 1, C.I. I. Pigment red 122, C.I. I. Pigment red 123, C.I. I. Pigment red 139, C.I. I. Pigment red 144, C.I. I. Pigment red 149, C.I. I. Pigment red 166, C.I. I. Pigment red 177, C.I. I. Pigment red 178, C.I. I. Pigment red 222, C.I. I. Pigment violet 19 and the like.

  Examples of organic pigments for green or cyan include C.I. I. Pigment blue 15, C.I. I. Pigment blue 15: 2, C.I. I. Pigment blue 15: 3, C.I. I. Pigment blue 15: 4, C.I. I. Pigment blue 16, C.I. I. Pigment blue 60, C.I. I. Pigment Green 7 and siloxane-crosslinked aluminum phthalocyanine described in US Pat. No. 4,311,775.

  Examples of organic pigments for black include C.I. I. Pigment black 1, C.I. I. Pigment black 6, C.I. I. Pigment black 7 and the like.

  The average particle diameter of the organic pigment is preferably as small as possible from the viewpoints of transparency and color reproducibility, but is preferably large from the viewpoint of light resistance. As an average particle diameter which makes these compatible, 10-200 nm is preferable, 10-150 nm is more preferable, 10-100 nm is still more preferable. In addition, the particle size distribution of the organic pigment is not particularly limited, and may be either a wide particle size distribution or a monodispersed particle size distribution. Two or more kinds of organic pigments having a monodispersed particle size distribution may be mixed and used.

  The addition amount of the organic pigment is preferably 1 to 25% by mass, more preferably 2 to 20% by mass, still more preferably 5 to 20% by mass, and particularly preferably 5 to 15% by mass with respect to the ink. preferable.

-Dispersant-
The organic pigment dispersant may be a polymer dispersant or a low molecular surfactant type dispersant. The polymer dispersant may be either a water-soluble dispersant or a water-insoluble dispersant.

  The low molecular surfactant type dispersant is added for the purpose of stably dispersing the organic pigment in an aqueous solvent while keeping the ink at a low viscosity. The low molecular dispersant is a low molecular dispersant having a molecular weight of 2,000 or less. The molecular weight of the low molecular dispersant is preferably 100 to 2,000, more preferably 200 to 2,000.

  The low molecular weight dispersant has a structure including a hydrophilic group and a hydrophobic group. In addition, the hydrophilic group and the hydrophobic group may be independently contained in one molecule or more, and may have a plurality of types of hydrophilic groups and hydrophobic groups. In addition, a linking group for linking a hydrophilic group and a hydrophobic group can be appropriately included.

  The hydrophilic group is anionic, cationic, nonionic, or a betaine type combining these.

  The anionic group may be any as long as it has a negative charge, but is preferably a phosphate group, phosphonic acid group, phosphinic acid group, sulfuric acid group, sulfonic acid group, sulfinic acid group or carboxylic acid group. More preferably a phosphoric acid group or a carboxylic acid group, and even more preferably a carboxylic acid group.

  The cationic group may be any as long as it has a positive charge, but is preferably an organic cationic substituent, and more preferably a nitrogen or phosphorus cationic group. Further, a pyridinium cation or an ammonium cation is more preferable.

  Examples of the nonionic group include polyethylene oxide, polyglycerin, a part of sugar unit, and the like.

  The hydrophilic group is preferably an anionic group. The anionic group is preferably a phosphoric acid group, a phosphonic acid group, a phosphinic acid group, a sulfuric acid group, a sulfonic acid group, a sulfinic acid group or a carboxylic acid group, more preferably a phosphoric acid group or a carboxylic acid group. More preferably, it is a carboxylic acid group.

Moreover, when a low molecular dispersing agent has an anionic hydrophilic group, it is preferable that pKa is 3 or more from a viewpoint of making it contact with an acidic process liquid and promoting an aggregation reaction. The pKa of the low molecular dispersant in the present invention is a low molecular dispersant 1 in a tetrahydrofuran-water (3: 2 = V / V) solution.
It is a value obtained by titrating a dissolved mol / L solution with an acid or alkaline solution and experimentally obtained from a titration curve. If the pKa of the low molecular dispersant is 3 or more, theoretically, 50% or more of the anionic groups are in a non-dissociated state when in contact with a treatment solution having a pH of about 3. Accordingly, the water solubility of the low molecular weight dispersant is remarkably lowered, and an agglomeration reaction occurs. That is, the aggregation reactivity is improved. Also from this viewpoint, the low molecular dispersant preferably has a carboxylic acid group as an anionic group.

The hydrophobic group has a hydrocarbon-based structure, a fluorocarbon-based structure, a silicone-based structure, or the like, and is particularly preferably a hydrocarbon-based structure. Further, these hydrophobic groups may have a linear structure or a branched structure. Further, the hydrophobic group may have a single chain structure or a chain structure of more than this, and in the case of a structure of two or more chains, it may have a plurality of types of hydrophobic groups.

  The hydrophobic group is preferably a hydrocarbon group having 2 to 24 carbon atoms, more preferably a hydrocarbon group having 4 to 24 carbon atoms, and still more preferably a hydrocarbon group having 6 to 20 carbon atoms.

  Among the polymer dispersants, as the water-soluble dispersant, a hydrophilic polymer compound can be used.For example, natural hydrophilic polymer compounds include gum arabic, tragan gum, guar gum, karaya gum, locust bean gum, arabinogalactone, Plant polymers such as pectin and quince seed starch, seaweed polymers such as alginic acid, carrageenan and agar, animal polymers such as gelatin, casein, albumin and collagen, and microbial polymers such as xanthene gum and dextran Can be mentioned.

  For hydrophilic polymer compounds modified from natural products, fiber polymers such as methylcellulose, ethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, and carboxymethylcellulose, starch starches such as sodium starch glycolate and sodium phosphate phosphate Examples include molecules, seaweed polymers such as sodium alginate and propylene glycol alginate.

  Examples of the synthetic water-soluble polymer compound include vinyl polymers such as polyvinyl alcohol, polyvinyl pyrrolidone, and polyvinyl methyl ether, non-crosslinked polyacrylamide, polyacrylic acid or alkali metal salts thereof, water-soluble styrene acrylic resins, and the like. Acrylic resin, water-soluble styrene maleic acid resin, water-soluble vinyl naphthalene acrylic resin, water-soluble vinyl naphthalene maleic resin, polyvinyl pyrrolidone, polyvinyl alcohol, alkali metal salts of β-naphthalene sulfonic acid formalin condensate, quaternary ammonium and amino And a polymer compound having a salt of a cationic functional group such as a group in the side chain, a natural polymer compound such as shellac, and the like.

  Among these, those having a carboxyl group introduced from a homopolymer of acrylic acid, methacrylic acid or styrene acrylic acid or a copolymer of a monomer having another hydrophilic group are particularly preferred as the polymer dispersant.

  As the water-insoluble dispersant among the polymer dispersants, a polymer having both a hydrophobic part and a hydrophilic part can be used. For example, styrene- (meth) acrylic acid copolymer, styrene- (meth) acrylic Acid- (meth) acrylic acid ester copolymer, (meth) acrylic acid ester- (meth) acrylic acid copolymer, polyethylene glycol (meth) acrylate- (meth) acrylic acid copolymer, vinyl acetate-maleic acid copolymer Examples thereof include a polymer and a styrene-maleic acid copolymer.

  The weight average molecular weight of the dispersant is preferably 3,000 to 100,000, more preferably 5,000 to 50,000, still more preferably 5,000 to 40,000, and particularly preferably 10,000 to 40,000. .

  The mixing mass ratio of the organic pigment and the dispersant is preferably in the range of 1: 0.06 to 1: 3, more preferably 1: 0.125 to 1: 2, and 1: 0.125 to 1: 1.5. Is more preferable.

-Water-soluble organic solvent-
The water-soluble organic solvent is used for the purpose of preventing drying and promoting wetting. Further, the drying inhibitor is suitably used at the ink ejection port of the nozzle in the ink jet recording method, and prevents clogging due to drying of the ink for ink jet.

  The drying inhibitor is preferably a water-soluble organic solvent having a vapor pressure lower than that of water. Specific examples of the drying inhibitor include ethylene glycol, propylene glycol, diethylene glycol, polyethylene glycol, thiodiglycol, dithiodiglycol, 2-methyl-1,3-propanediol, 1,2,6-hexanetriol, Polyhydric alcohols represented by acetylene glycol derivatives, glycerin, trimethylolpropane, etc., polyvalent alcohols such as ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, triethylene glycol monoethyl (or butyl) ether Lower alkyl ethers of alcohols, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, heterocyclic rings such as N-ethylmorpholine, sulfolane, dimethyls Sulfoxide, sulfur-containing compounds such as 3-sulfolene, diacetone alcohol, polyfunctional compounds such as diethanolamine, and urea derivatives. Of these, the drying inhibitor is preferably a polyhydric alcohol such as glycerin or diethylene glycol. Moreover, said anti-drying agent may be used independently or may be used together 2 or more types. These drying inhibitors are preferably contained in the ink in an amount of 10 to 50% by mass.

  Further, the penetration enhancer is preferably used for the purpose of allowing the ink to penetrate better into the recording medium (printing paper). Specific examples of penetration enhancers include alcohols such as ethanol, isopropanol, butanol, di (tri) ethylene glycol monobutyl ether, 1,2-hexanediol, sodium lauryl sulfate, sodium oleate, and nonionic surfactants. Etc. can be used suitably. These penetration enhancers exhibit a sufficient effect when contained in the ink composition in an amount of 5 to 30% by mass. Further, it is preferable that the penetration enhancer is used within a range of an addition amount that does not cause printing bleeding and paper loss (print through).

  In addition to the above, the water-soluble organic solvent is also used for adjusting the viscosity. Specific examples of water-soluble organic solvents that can be used to adjust the viscosity include alcohols (eg, methanol, ethanol, propanol, isopropanol, butanol, isobutanol, sec-butanol, t-butanol, pentanol, hexanol, Cyclohexanol, benzyl alcohol), polyhydric alcohols (for example, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, polypropylene glycol, butylene glycol, hexanediol, pentanediol, glycerin, hexanetriol, Thiodiglycol), glycol derivatives (eg, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether) Ter, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monobutyl ether, dipropylene glycol monomethyl ether, triethylene glycol monomethyl ether, ethylene glycol diacetate, ethylene glycol monomethyl ether acetate, Triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, ethylene glycol monophenyl ether), amine (eg, ethanolamine, diethanolamine, triethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, morpholine, N-ethylmorpholine, Tylenediamine, diethylenetriamine, triethylenetetramine, polyethyleneimine, tetramethylpropylenediamine) and other polar solvents (eg, formamide, N, N-dimethylformamide, N, N-dimethylacetamide, dimethylsulfoxide, sulfolane, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, 2-oxazolidone, 1,3-dimethyl-2-imidazolidinone, acetonitrile, acetone). In addition, a water-soluble organic solvent may be used independently and may use 2 or more types together.

-Other additives-
Examples of the other additives include a drying inhibitor (wetting agent), an antifading agent, an emulsion stabilizer, a penetration accelerator, an ultraviolet absorber, an antiseptic, an antifungal agent, a pH adjuster, a surface tension adjuster, Well-known additives, such as an antifoamer, a viscosity modifier, a dispersing agent, a dispersion stabilizer, an antirust agent, a chelating agent, are mentioned. In the case of water-soluble ink, these various additives are added directly to the ink. When an oil-soluble dye is used in the form of a dispersion, it is generally added to the dispersion after the preparation of the dye dispersion, but it may be added to the oil phase or the aqueous phase at the time of preparation.

  The ultraviolet absorber is used for the purpose of improving image storability. Examples of ultraviolet absorbers include benzotriazoles described in JP-A Nos. 58-185677, 61-190537, JP-A-2-782, JP-A-5-97075, JP-A-9-34057, and the like. Compounds, benzophenone compounds described in JP-A No. 46-2784, JP-A No. 5-194433, US Pat. No. 3,214,463, etc., JP-B Nos. 48-30492, 56-211141, Cinnamic acid compounds described in, for example, Kaihei 10-88106, JP-A-4-298503, 8-53427, 8-239368, 10-182621, JP-A-8- No. 501291, etc., triazine compounds, Research Disclosure No. Compounds described in No. 24239, compounds that emit fluorescence by absorbing ultraviolet rays typified by stilbene-based and benzoxazole-based compounds, so-called fluorescent brighteners, can also be used.

  The anti-fading agent is used for the purpose of improving image storage stability. As the antifading agent, various organic and metal complex antifading agents can be used. Organic anti-fading agents include hydroquinones, alkoxyphenols, dialkoxyphenols, phenols, anilines, amines, indanes, chromans, alkoxyanilines, heterocycles, etc. Complex, zinc complex and the like. More specifically, Research Disclosure No. No. 17643, No. VII, I to J, ibid. 15162, ibid. No. 18716, page 650, left column, ibid. No. 36544, page 527, ibid. No. 307105, page 872, ibid. The compounds described in the patent cited in Japanese Patent No. 15162 and the compounds included in the general formulas and compound examples of typical compounds described on pages 127 to 137 of JP-A-62-215272 can be used.

  Examples of the antifungal agent include sodium dehydroacetate, sodium benzoate, sodium pyridinethione-1-oxide, p-hydroxybenzoic acid ethyl ester, 1,2-benzisothiazolin-3-one and salts thereof. These are preferably used in the ink in an amount of 0.02 to 1.00% by mass.

  As the pH adjuster, a neutralizer (organic base, inorganic alkali) can be used. For the purpose of improving the storage stability of the inkjet ink, the pH adjuster is preferably added so that the inkjet ink has a pH of 6 to 10, and more preferably added to have a pH of 7 to 10.

  Examples of the surface tension adjusting agent include nonionic surfactants, cationic surfactants, anionic surfactants, betaine surfactants, and the like.

  In addition, the addition amount of the surface tension adjusting agent is preferably an addition amount that adjusts the surface tension of the ink to 20 to 60 mN / m, and preferably an addition amount that is adjusted to 20 to 45 mN / m, in order to eject droplets well by inkjet. More preferable is an addition amount adjusted to 25 to 40 mN / m.

  Specific examples of surfactants include fatty acid salts, alkyl sulfate esters, alkylbenzene sulfonates, alkyl naphthalene sulfonates, dialkyl sulfosuccinates, alkyl phosphate esters, naphthalene sulfonate formalin condensation in hydrocarbons. Products, anionic surfactants such as polyoxyethylene alkyl sulfates, polyoxyethylene alkyl ethers, polyoxyethylene alkyl allyl ethers, polyoxyethylene fatty acid esters, sorbitan fatty acid esters, polyoxyethylene sorbitan fatty acid esters, polyoxy Nonionic surfactants such as ethylene alkylamine, glycerin fatty acid ester and oxyethyleneoxypropylene block copolymer are preferred. Further, SURFYNOLS (Air Products & Chemicals), which is an acetylene-based polyoxyethylene oxide surfactant, is also preferably used. An amine oxide type amphoteric surfactant such as N, N-dimethyl-N-alkylamine oxide is also preferred.

  Furthermore, pages (37) to (38) of JP-A-59-157636, Research Disclosure No. The surfactants described in 308119 (1989) can also be used.

  Further, fluorine (fluorinated alkyl) -based surfactants and silicone-based surfactants as described in JP-A-2003-322926, JP-A-2004-325707, JP-A-2004-309806, etc. Etc. can be used to improve the abrasion resistance.

  These surface tension modifiers can also be used as antifoaming agents, and fluorine compounds, silicone compounds, chelating agents represented by EDTA, and the like can also be used.

Examples of the present invention will be described below, but the present invention is not limited to the following examples.
In the examples, “parts” and “%” are based on mass unless otherwise specified, and “polymerization degree” represents “average polymerization degree”.

Example 1
<Preparation of coating liquid for first layer (undercoat layer)>
(1) Preparation of acetoacetyl-modified polyvinyl alcohol 12 acetoacetyl-modified polyvinyl alcohol (degree of saponification: 95 to 97%, degree of polymerization: 1,000, trade name: Goosefima-Z-210, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) And 88 parts of water were added and dissolved by stirring at 90 ° C. or higher.
(2) Water-swellable mica dispersion (aspect ratio: 1,000, trade name: Somasif MEB-3 (8% solution), manufactured by Co-op Chemical Co., Ltd., mica dispersion having an average particle size of 2.0 μm).
(3) 1.66% solution of ethylene oxide surfactant (trade name: Emalex 710, manufactured by Nippon Emulsion Co., Ltd.)

  To 100 parts of the 12% acetoacetyl-modified polyvinyl alcohol solution of (1) above, 58 parts of water is added and mixed with sufficient stirring, and 18 parts of 8% water-swellable mica dispersion of (2) above is added with sufficient stirring and mixing. Then, 3 parts of the 1.66% ethylene oxide surfactant solution of (3) was added. The liquid temperature of the obtained mixed liquid was kept at 30 ° C. to 35 ° C. to obtain an undercoat layer coating liquid.

<Preparation of coating solution for second layer (overcoat layer)>
60 parts of heavy calcium carbonate (trade name: Escalon # 2000, Sankyo Seimitsu Co., Ltd.), 20 parts of kaolin (trade name: Milagros, Engelhard Inc .: USA), titanium oxide (Typaque R-780, Ishihara Sangyo) 20 parts) and 43 parts of 43% sodium polyacrylate (trade name: Aron T-50, manufactured by Toagosei Co., Ltd.) are mixed, and NBK-2 manufactured by Nippon Seiki Seisakusho Co., Ltd. is used. 11 parts of styrene-butadiene copolymer latex (trade name: SMARTEX PA2323, manufactured by Nippon A & L Co., Ltd.) dispersed in water and having an average particle size of 95 nm, and oxidized starch (trade name: ACE B, manufactured by Oji Cornstarch Co., Ltd.) 3 Part and a lubricant (trade name: SN coat 231SP, manufactured by San Nopco Co., Ltd.) are added to prepare an overcoat layer coating solution with a final solid content concentration of 65%. .

<Formation of first layer (undercoat layer)>
Using a bar coater, apply the coating solution for the undercoat layer obtained on both sides of high-quality paper (trade name: Shiraoi, manufactured by Nippon Paper Industries Co., Ltd.) with a basis weight of 81.4 g / m ^2. Was applied to each side while adjusting to be 8.0 g / m ² and dried at 50 ° C. for 3 minutes to form an undercoat layer. Here, the thickness of the formed undercoat layer was 8.1 μm.

<Formation of second layer (overcoat layer)>
Using the high-speed sheet-fed blade coater (apparatus name: PM-9040M, manufactured by SMT Co., Ltd.), the prepared coating liquid for the overcoat layer is applied to both sides of the fine paper on which the undercoat layer is formed. One side was applied while adjusting the dry mass to 10 g / m ² and dried at a temperature of 150 ° C. and a wind speed of 20 m / sec for 3 seconds to form an overcoat layer. At this time, the thickness of the formed overcoat layer per one surface was 11.2 μm.

<Evaluation of recording medium>
About the recording medium obtained in Example 1, “Cobb water absorption test of fine paper with an undercoat layer”, “Water absorption test of topcoat layer”, “Curl test”, “Drip test”, “Just after printing” "Cuckle test" and "Density unevenness test" were conducted as shown below. The results are shown in Table 1.

-Cobb water absorption test of fine paper with undercoat layer-
(1) In accordance with the water absorption test specified in JIS P8140, the coated surface of the fine paper on which the undercoat layer is formed has a Cobb water absorption (the amount of water permeation when contacting with water at 20 ° C. for 15 seconds g / m ² ) was measured.
(2) In accordance with the water absorption test specified in JIS P8140, the Cobb water absorption on the coated surface of the fine paper on which the undercoat layer was formed (the amount of water penetration when contacting with water at 20 ° C. for 2 minutes g / m ² ) was measured.
(3) In accordance with the water absorption test specified in JIS P8140, the coated surface of the fine paper on which the undercoat layer is formed has a Cobb value (the penetration amount of diethylene glycol when brought into contact with diethylene glycol at 20 ° C. for 2 minutes, g / m ² ) was measured.

-Water absorption test of topcoat layer-
Based on the Bristow method, measurements were made as follows.
(1) An overcoat layer cut to A6 size is placed on a measuring board, and after touching a head filled with a test solution, a scanning line (from inside to outside) as shown in FIG. It was measured. The measurement board changes the rotation speed (contact time between paper and ink) stepwise and rotates to obtain the relationship between the contact time and the liquid absorption amount (water absorption amount). Table 1 shows the water absorption amount at a contact time of 0.5 seconds.
(2) Measurement was performed in the same manner except that the water of (1) was changed to pure water containing 30% by mass of diethylene glycol. Table 1 shows the liquid absorption amount at a contact time of 0.9 seconds.

-Method for measuring high shear viscosity of coating liquid for topcoat layer-
For the high shear viscosity, use a Hercules High Shear Viscometer (Hercules High Shear Viscometer: manufactured by Kumagai Riki Kogyo Co., Ltd.) and put an appropriate amount of the coating liquid for the topcoat layer in a cup with an inner diameter of 40 mm and an effective depth of 80.5 mm. Using Bob F (rotary body) with a diameter of 39.8 mm and an effective length of 25 mm (with a clearance of 0.1 mm from the cup), the sweep time is set to 10 seconds, and the maximum rotational speed is 8,800 rpm. [Shear Measure (Rotational Speed)]-[Shear Stress (Torque)] Curve) was determined, and apparent viscosity was determined from this.

-Glossy evaluation of white paper-
About the white background, in accordance with JIS Z8741 (1997), using a digital variable gloss meter (trade name: UGV-5D, manufactured by Suga Test Instruments Co., Ltd.), the glossiness at an incident angle of 75 ° and a light receiving angle of 75 ° Was measured and evaluated according to the following criteria.
〔Evaluation criteria〕
AA: Glossiness was 50% or more BB: Glossiness was 35% or more and less than 50% CC: Glossiness was 20% or more and less than 35% DD: Glossiness was less than 20%

-Curl test-
For the recording medium on which the second layer (overcoat layer) was formed, water was applied to a test piece of 50 mm × 5 mm size in the MD and CD directions so that the water would be 10 g / m ^2, and the JAPAN TAPPI paper pulp test Method No. Based on the curl curvature measuring method prescribed | regulated to 15-2: 2000, the curl degree after 8 hours and 50% RH was measured in accordance with the following reference | standard at 23 degreeC.
〔Evaluation criteria〕
AAA: curl degree of less than 5 AA: curl degree of 5 or more and less than 10 BB: curl degree of 10 or more and less than 20 CC: curl degree of 20 or more and less than 30 DD: curl degree of 30 or more

-Evaluation of cockle immediately after printing-
A 2cm x 2cm single color 100% solid image is printed on the center of a postcard on a recording medium with a postcard-size topcoat layer, and the maximum height of the corrugation generated immediately after printing is measured with a laser displacement meter. It was evaluated with.
[Evaluation criteria]
AA: 1 mm or more and less than 2 mm BB: 2 mm or more and less than 3 mm CC: 3 mm or more

-Evaluation of density unevenness-
A single-color 100% solid image printed for evaluation of cockle was visually evaluated according to the following criteria.
[Evaluation criteria]
AA: Solid image area density is uniform, white spots are not observed at all, and printing spots are not observed at all. BB: White spots, printing spots are somewhat, but there is no problem in practical use. CC: White spots, printing spots are seen a lot, practicality Low DD: White spots, severe print spots, extremely low utility

-Droplet test-
<Preparation of ink>

(1) Preparation of Cyan Pigment Ink C-Preparation of Pigment Dispersion-
10 g of Cyanine Blue A-22 (CI.PB15: 3) manufactured by Dainichi Seika Co., Ltd., low molecular weight dispersant 2-1, 10.0 g, 4.0 g of glycerin, and 26 g of ion-exchanged water were mixed with stirring to obtain a dispersion. Was prepared. Next, using an ultrasonic irradiation device (SONICS Vibra-cell VC-750, tapered microchip: φ5 mm, Amplitude: 30%), the dispersion is intermittently irradiated with ultrasonic waves (irradiation 0.5 seconds, pause) (1.0 second) for 2 hours to further disperse the pigment to obtain a 20% by mass pigment dispersion. The low molecular weight dispersant 2-1 is represented by the following chemical formula.
Separately from the above, the compound shown below was weighed, stirred and mixed to prepare a mixed solution I.
Glycerin 5.0g
Diethylene glycol 10.0g
Olfin E1010 (Nissin Chemical Industry) 1.0g
Ion exchange water 11.0g
The mixture I was slowly added dropwise to 23.0 g of a stirred 44% SBR dispersion (polymer fine particles: 3% by mass of acrylic acid, Tg (glass transition temperature) 30 ° C.), and mixed by stirring. Prepared.
Further, 100 g of cyan pigment ink C (cyan ink) was prepared by stirring and mixing the mixed solution II while slowly dropping into the 20% pigment dispersion described above. Using the pH meter WM-50EG manufactured by Toa DKK Co., Ltd., the pH of the pigment ink C prepared in this way was measured, and the pH value was 8.5.

(2) Preparation of Magenta Pigment Ink M Instead of the pigment used in the preparation of Pigment Ink C, Chromatic Jet Magenta DMQ (PR-122) manufactured by Ciba Specialty Chemicals was used. Except for the pigment, a magenta pigment ink M (magenta ink) was prepared in the same manner as the preparation of the pigment ink C described above. When the pH of the pigment ink M thus prepared was measured with a pH meter WM-50EG manufactured by Toa DKK, the pH value was 8.5.

(3) Preparation of Yellow Pigment Ink Y In place of the pigment used in the preparation of Pigment Ink C, Irgalite Yellow GS (C.I.PY74) manufactured by Ciba Specialty Chemicals was used. Except for the pigment, yellow pigment ink Y (yellow ink) was prepared in the same manner as in the preparation of pigment ink C described above. When the pH of the pigment ink Y thus prepared was measured with a pH meter WM-50EG manufactured by Toa DKK, the pH value was 8.5.

(4) Preparation of Black Pigment Ink K Similar to the preparation of Pigment Ink C described above, except that the pigment dispersion used for the preparation of Pigment Ink C was a dispersion CAB-O-JETTM_200 (carbon black) manufactured by CABOT. The black pigment ink K (black ink) was prepared by the method described above. When the pH of the pigment ink K thus prepared was measured with a pH meter WM-50EG manufactured by Toa DKK Co., Ltd., the pH value was 8.5.

<Preparation of treatment liquid>
The treatment liquid was prepared by mixing the following materials.
・ Phosphoric acid 10g
・ Glycerin 20g
・ Diethylene glycol 10g
・ Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 1g
・ Ion exchange water 59g
When the pH of the first treatment liquid thus prepared was measured with a pH meter WM-50EG manufactured by Toa DKK, the pH value was 1.0.

<Dropping method>
Using the cyan pigment ink C, magenta pigment ink M, yellow pigment ink Y, black pigment ink K, and processing liquid, four-color single-pass image formation was performed using the apparatus shown in FIG. 3 under the following conditions.

--- Treatment liquid head for precoat module-
Head: 600 dpi / 20 inch width piezo-full line head Discharge droplet volume: 0, 4.0 pL binary recording Drive frequency: 15 kHz (recording medium conveyance speed 635 mm / sec)
Drawing pattern: In the ink drawing process, a pattern that applies treatment liquid in advance to the position where drawing is performed with at least one color ink is applied.

--- Water drying for precoat module (blow drying)-
Wind speed: 15m / s
Temperature: Heated from the back surface of the recording medium recording surface with a contact type flat heater so that the surface temperature of the recording medium becomes 60 ° C. Air blowing area: 450 mm (drying time 0.7 seconds)

--Ink drawing--
Head: 1,200 dpi / 20 inch width piezo full line head is arranged for 4 colors. Ejected droplet volume: 4-value recording of 0, 2.0, 3.5, 4.0 pL Drive frequency: 30 kHz (Recording medium transport speed 635 mm / sec)

-Drying (water drying, blow drying)-
Wind speed: 15m / s
Temperature: 60 ° C
Air blowing area: 640 mm (drying time 1 second)

--Fixing--
Silicone rubber roller (hardness 50 °, nip width 5mm)
Roller temperature: 90 ° C
Pressure: 0.8 MPa

<Evaluation method>
The gray scale and the character image printed for evaluation were visually evaluated according to the following criteria.
[Evaluation criteria]
AA: No image blur or inter-color mixing is observed, and “hawk” characters of 4 pt or less are resolved BB: Image blur, inter-color mixing is not observed, and 5 pt “hawk” characters are resolved CC: Image blur, color There are many intermixing colors and the practicality is low. DD: Image blur, intercolor mixing is severe, and the practicality is extremely low.

(Example 2)
In the preparation of the coating solution for the undercoat layer in Example 1, acetoacetyl-modified polyvinyl alcohol (degree of saponification: 95 to 97%, degree of polymerization: 1,000, trade name: Goosefima-Z-210, Nippon Synthetic Chemical Industry Co., Ltd. Instead of using polyvinyl alcohol (degree of saponification: 98.5%, degree of polymerization: 1,700, trade name: PVA-117, manufactured by Kuraray Co., Ltd.) except for changing the coating amount per one side of the top coat layer coating solution from 11.2 g / m ² to 10.8 g / m ^2, the a recording medium was prepared in the same manner as in example 1. Here, the thickness of the formed undercoat layer was 8.0 μm, and the thickness of the formed overcoat layer was 11.0 μm. In addition, as in Example 1, “Cobb water absorption test of fine paper with an undercoat layer”, “Water absorption test of topcoat layer”, “High shear viscosity measurement of coating liquid for topcoat layer”, “Blank paper” “Gloss evaluation”, “curl test”, “droplet test (evaluated by the same method as in Example 1)”, “cuckle test immediately after printing”, and “density unevenness test” were performed. The results are shown in Table 1.

(Example 3)
12.0 parts of a 4% aqueous solution of 2-ethylenesulfonyl-N- [2- (2-ethylenesulfonyl-acetylamino) -ethyl] -acetamide as a hardener solution in the undercoat layer coating solution in Example 1 Was further added to obtain 7.3% of the undercoat layer coating solution, and in the formation of the undercoat layer in Example 1, the coating amount per side of the undercoat layer coating solution was 8.0 g / m ^2. was changed to 5.0 g / ^{m 2} from and, in the formation of the overcoat layer in example 1, 10.1 g / m and coated amount per one surface from 11.2 g / ^{m 2} of the top coat layer coating solution ^A recording medium was produced in the same manner as in Example 1 except that it was changed to ² . Here, the thickness of the formed undercoat layer was 4.8 μm, and the thickness of the formed overcoat layer was 10.1 μm. In addition, as in Example 1, “Cobb water absorption test of fine paper with an undercoat layer”, “Water absorption test of topcoat layer”, “High shear viscosity measurement of coating liquid for topcoat layer”, “Blank paper” A gloss evaluation, a curl test, a droplet ejection test, a cockle test immediately after printing, and a density unevenness test were performed. The results are shown in Table 1.

Example 4
In the preparation of the coating solution for the undercoat layer of Example 3, a 4% aqueous solution of 2-ethylenesulfonyl-N- [2- (2-ethylenesulfonyl-acetylamino) -ethyl] -acetamide as a hardener solution. A recording medium was produced in the same manner as in Example 3 except that 0 part was changed to 24.0 parts of a 50% aqueous solution of 2,3-dihydroxy-5-methyl-1,4-dioxane. Here, the thickness of the formed undercoat layer was 3.5 μm, and the thickness of the formed overcoat layer was 12.3 μm. In addition, as in Example 3, “Cobb water absorption test of fine paper with an undercoat layer”, “Water absorption test of topcoat layer”, “High shear viscosity measurement of coating solution for topcoat layer”, “Blank paper” A gloss evaluation, a curl test, a droplet ejection test, a cockle test immediately after printing, and a density unevenness test were performed. The results are shown in Table 1.

(Example 5)
2. In the preparation of the undercoat layer coating solution of Example 3, a 4% aqueous solution of 2-ethylenesulfonyl-N- [2- (2-ethylenesulfonyl-acetylamino) -ethyl] -acetamide as a hardener solution. A recording medium was produced in the same manner as in Example 3 except that 0 part was changed to 15.0 parts of a 40% aqueous solution of glyoxal. Here, the thickness of the formed undercoat layer was 5.2 μm, and the thickness of the formed overcoat layer was 9.9 μm. In addition, as in Example 3, “Cobb water absorption test of fine paper with an undercoat layer”, “Water absorption test of topcoat layer”, “High shear viscosity measurement of coating solution for topcoat layer”, “Blank paper” A gloss evaluation, a curl test, a droplet ejection test, a cockle test immediately after printing, and a density unevenness test were performed. The results are shown in Table 1.

(Example 6)
“Preparation of coating solution for undercoat layer” and “Formation of undercoat layer” in Example 1 were changed as follows, and the coating amount per one side of the coating solution for undercoat layer was 8.0 g / m ^2. A recording medium was produced in the same manner as in Example 1 except that it was changed from 10.0 to 10.0 g / m ² and the soft calendar process was performed. Here, the thickness of the formed undercoat layer was 9.7 μm, and the thickness of the formed overcoat layer was 9.0 μm. In addition, as in Example 1, “Cobb water absorption test of fine paper with an undercoat layer”, “Water absorption test of topcoat layer”, “High shear viscosity measurement of coating liquid for topcoat layer”, “Blank paper” A gloss evaluation, a curl test, a droplet ejection test, a cockle test immediately after printing, and a density unevenness test were performed. The results are shown in Table 1.

<Preparation of coating solution for undercoat layer>
100 parts of titanium dioxide (trade name: Taipei R-780, manufactured by Ishihara Sangyo Co., Ltd.), 25% Na salt of special polycarboxylic acid type polymer (trade name: Demol EP, manufactured by Kao Corporation) 1.2 Part and water 121.7 parts were mixed and dispersed using a non-bubbling kneader (trade name: NBK-2, manufactured by Nippon Seiki Seisakusho Co., Ltd.) to obtain a 45% titanium dioxide dispersion. Subsequently, 100 parts of water is obtained in 100 parts of 35% acrylic latex aqueous dispersion (glass transition temperature 60 ° C., minimum film forming temperature 50 ° C .; trade name: Aquabrid 4635, manufactured by Daicel Chemical Industries, Ltd.). After adding 3.9 parts of 45% titanium dioxide dispersion and stirring and mixing sufficiently, the liquid temperature of the obtained mixed liquid was kept at 15 to 25 ° C. and 18.0% undercoat layer coating liquid. Got.

<Formation of undercoat layer>
Using a bar coater, apply the coating solution for the undercoat layer obtained on both sides of high-quality paper (trade name: Shiraoi, manufactured by Nippon Paper Industries Co., Ltd.) with a basis weight of 81.4 g / m ^2. Was applied to each side while adjusting so as to be 10.0 g / m ² and dried at 50 ° C. for 3 minutes to form an undercoat layer. Furthermore, the soft calendar process shown below was performed with respect to the formed undercoat.

-Soft calendar processing-
Using a soft calender provided with a roll pair in which a metal roll and a resin roll are paired with respect to the high-quality paper having the undercoat layer formed on the surface, the surface temperature of the metal roll is 80 ° C., the nip pressure is 100 kg / cm, and the speed Soft calendering was performed under the condition of 100 m / min.

(Example 7)
In the preparation of the coating liquid for the undercoat layer of Example 6, 35% acrylic latex aqueous dispersion was changed to 35% acrylic silicone latex aqueous dispersion (glass transition temperature 25 ° C., minimum film forming temperature 20 ° C .; A recording medium was produced in the same manner as in Example 6 except that the name was changed to “Aquabrid ASi-91, manufactured by Daicel Chemical Industries, Ltd.”. Here, the thickness of the formed undercoat layer was 9.9 μm, and the thickness of the formed overcoat layer was 9.3 μm. In addition, as in Example 6, “Cobb water absorption test of fine paper on which undercoat layer was formed”, “Water absorption test of topcoat layer”, “High shear viscosity measurement of coating liquid for topcoat layer”, “Blank paper” A gloss evaluation, a curl test, a droplet ejection test, a cockle test immediately after printing, and a density unevenness test were performed. The results are shown in Table 1.

(Example 8)
In “Preparation of coating solution for undercoat layer” and “Preparation of undercoat layer” in Example 6, 35% acrylic latex aqueous dispersion was mixed with 35% acrylic epoxy latex (minimum film-forming temperature 40 ° C .; trade name : Aquabrid AEA-61, manufactured by Daicel Chemical Industries, Ltd.), and a recording medium was produced in the same manner as in Example 6 except that the soft calendar process was not performed. Here, the thickness of the formed undercoat layer was 10.1 μm, and the thickness of the formed overcoat layer was 9.4 μm. In addition, as in Example 6, “Cobb water absorption test of fine paper on which undercoat layer was formed”, “Water absorption test of topcoat layer”, “High shear viscosity measurement of coating liquid for topcoat layer”, “Blank paper” “Glossiness evaluation”, “curl test”, “droplet test”, “cuckle test immediately after printing”, and “density unevenness test” were performed. The results are shown in Table 1.

Example 9
In Example 6 “Preparation of undercoat layer coating solution” and “Preparation of undercoat layer”, 35% acrylic latex aqueous dispersion was treated with 35% acrylic urethane latex (minimum film forming temperature 0 ° C .; product Name: Aquabrid AU-124, manufactured by Daicel Chemical Industries, Ltd.) A recording medium was prepared in the same manner as in Example 6 except that the soft calendar process was not performed. Here, the thickness of the formed undercoat layer was 9.5 μm, and the thickness of the formed overcoat layer was 9.3 μm. In addition, as in Example 6, “Cobb water absorption test of fine paper on which undercoat layer was formed”, “Water absorption test of topcoat layer”, “High shear viscosity measurement of coating solution for topcoat layer”, “Blank paper” A gloss evaluation, a curl test, a droplet ejection test, a cockle test immediately after printing, and a density unevenness test were performed. The results are shown in Table 1.

(Example 10)
In “Preparation of undercoat layer coating solution” and “Preparation of undercoat layer” in Example 6, 35% acrylic latex aqueous dispersion was mixed with 35% styrene-butadiene latex (minimum film forming temperature 0 ° C .; A recording medium was produced in the same manner as in Example 6 except that the product name was changed to Nipol LX110 (manufactured by Zeon Corporation) and that the soft calendar process was not performed. Here, the thickness of the formed undercoat layer was 9.4 μm, and the thickness of the formed overcoat layer was 9.5 μm. In addition, as in Example 6, “Cobb water absorption test of fine paper on which undercoat layer was formed”, “Water absorption test of topcoat layer”, “High shear viscosity measurement of coating solution for topcoat layer”, “Blank paper” “Glossiness evaluation”, “curl test”, “droplet test”, “cuckle test immediately after printing”, and “density unevenness test” were performed. The results are shown in Table 1.

(Example 11)
In “Preparation of coating solution for undercoat layer” and “Preparation of undercoat layer” in Example 6, 35% acrylic latex aqueous dispersion was mixed with 35% acrylonitrile-butadiene latex (minimum film forming temperature 0 ° C .; product Name: Nipol 1561 (manufactured by Nippon Zeon Co., Ltd.) A recording medium was produced in the same manner as in Example 6 except that the soft calendar process was not performed. Here, the thickness of the formed undercoat layer was 10.2 μm, and the thickness of the formed overcoat layer was 9.3 μm. In addition, as in Example 6, “Cobb water absorption test of fine paper on which undercoat layer was formed”, “Water absorption test of topcoat layer”, “High shear viscosity measurement of coating liquid for topcoat layer”, “Blank paper” A gloss evaluation, a curl test, a droplet ejection test, a cockle test immediately after printing, and a density unevenness test were performed. The results are shown in Table 1.

Example 12
A recording medium was prepared in the same manner as in Example 6 except that in the preparation of the undercoat layer coating solution of Example 6, 3.9 parts of 45% titanium dioxide dispersion was replaced with 8.6 parts. Here, the thickness of the formed undercoat layer was 9.0 μm, and the thickness of the formed overcoat layer was 9.6 μm. In addition, as in Example 1, “Cobb water absorption test of fine paper with an undercoat layer”, “Water absorption test of topcoat layer”, “High shear viscosity measurement of coating liquid for topcoat layer”, “Blank paper” A gloss evaluation, a curl test, a droplet ejection test, a cockle test immediately after printing, and a density unevenness test were performed. The results are shown in Table 1.

(Example 13)
<Preparation of coating liquid for first layer (undercoat layer)>
(1) Preparation of acetoacetyl-modified polyvinyl alcohol 12 acetoacetyl-modified polyvinyl alcohol (degree of saponification: 95 to 97%, degree of polymerization: 1,000, trade name: Goosefima-Z-210, manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) And 88 parts of water were added and dissolved by stirring at 90 ° C. or higher.
(2) 50% aqueous solution of 2,3-dihydroxy-5-methyl-1,4-dioxane (3) Ethylene oxide surfactant (trade name: Emalex 710, manufactured by Nippon Emulsion Co., Ltd.) 1.66% by mass liquid (Methanol dissolution).

  To 100 parts of the 12% acetoacetyl-modified polyvinyl alcohol solution of (1) above, 58 parts of water was added and mixed with sufficient stirring, and 50 parts of 2,3-dihydroxy-5-methyl-1,4-dioxane of (2) were mixed. 24 parts of a% aqueous solution was added and sufficiently mixed by stirring, and 3 parts of the 1.66 mass% ethylene oxide surfactant solution of (3) above was added. The liquid temperature of the obtained mixed liquid was kept at 30 ° C. to 35 ° C. to obtain an undercoat layer coating liquid.

<Preparation of coating solution for second layer (overcoat layer)>
40 parts of heavy calcium carbonate (trade name: Escalon # 2000, Sankyo Seimitsu Co., Ltd.), 40 parts of kaolin (trade name: Milagros, Engelhard Inc .: USA), titanium oxide (Typaque R-780, Ishihara Sangyo) 20 parts) and 43 parts of 43% sodium polyacrylate (trade name: Aron T-50, manufactured by Toagosei Co., Ltd.) are mixed, and NBK-2 manufactured by Nippon Seiki Seisakusho Co., Ltd. is used. 13 parts of a styrene-butadiene copolymer latex (trade name: SMARTEX PA2323, manufactured by Nippon A & L Co.) having an average particle size of 95 nm dispersed in water, and oxidized starch (trade name: ACE B, manufactured by Oji Cornstarch Co., Ltd.) 3 Part and a lubricant (trade name: SN coat 231SP, manufactured by San Nopco Co., Ltd.) are added to prepare an overcoat layer coating solution with a final solid content concentration of 65%. .

<Formation of first layer (undercoat layer)>
Using a bar coater, apply the coating solution for the undercoat layer obtained on both sides of high-quality paper (trade name: Shiraoi, manufactured by Nippon Paper Industries Co., Ltd.) with a basis weight of 81.4 g / m ^2. Was adjusted to 3.5 g / m ² one side at a time and dried at 50 ° C. for 3 minutes to form an undercoat layer. Here, the thickness of the formed undercoat layer was 3.4 μm.

<Formation of second layer (overcoat layer)>
Using the high-speed sheet-fed blade coater (apparatus name: PM-9040M, manufactured by SMT Co., Ltd.), the prepared coating liquid for the overcoat layer is applied to both sides of the fine paper on which the undercoat layer is formed. One side was applied while adjusting the dry mass to 10 g / m ² and dried at a temperature of 150 ° C. and a wind speed of 20 m / sec for 3 seconds to form an overcoat layer. At this time, the thickness of the formed overcoat layer per one surface was 10.3 μm. In addition, as in Example 1, “Cobb water absorption test of fine paper with an undercoat layer”, “Water absorption test of topcoat layer”, “High shear viscosity measurement of coating liquid for topcoat layer”, “Blank paper” A gloss evaluation, a curl test, a droplet ejection test, a cockle test immediately after printing, and a density unevenness test were performed. The results are shown in Table 1.

(Example 14)
In the preparation of the coating solution for the topcoat layer of Example 13, 40 parts of heavy calcium carbonate (trade name: Escalon # 2000, manufactured by Sankyo Seimitsu Co., Ltd.), kaolin (trade name: Milagros, manufactured by Engelhard Inc .: USA) 40 And 13 parts of styrene-butadiene copolymer latex (trade name: SMARTEX PA2323, manufactured by Nippon A & L Co.) having an average particle size of 95 nm, instead of heavy calcium carbonate (trade name: ESCALON # 2000, Sankyo) 70 parts by Seiko Co., Ltd., 10 parts by kaolin (trade name: Milagros, Engelhard: USA), styrene-butadiene copolymer latex having a mean particle size of 95 nm (trade name: SMARTEX PA2323, manufactured by Nippon A & L Co., Ltd.) ) A recording medium was produced in the same manner as in Example 13 except that 9 parts were used. Here, the thickness of the formed undercoat layer was 3.5 μm, and the thickness of the formed overcoat layer was 10.5 μm. In addition, as in Example 13, “Cobb water absorption test of fine paper with an undercoat layer”, “Water absorption test of topcoat layer”, “Measurement of high shear viscosity of coating liquid for topcoat layer”, “Blank paper” A gloss evaluation, a curl test, a droplet ejection test, a cockle test immediately after printing, and a density unevenness test were performed. The results are shown in Table 1.

(Example 15)
A recording medium was produced in the same manner as in Example 4 except that “Preparation of coating liquid for topcoat layer” in Example 4 was changed as described below.

<Preparation of ink absorbing layer (overcoat layer) coating solution>
10 parts of kaolin (trade name: Milagros, manufactured by Engelhard: USA), 90 parts of titanium oxide (Taipeke R-780, manufactured by Ishihara Sangyo Co., Ltd.), and 43% sodium polyacrylate (trade name: Aron T-50) Styrene-butadiene copolymer latex having a mean particle size of 95 nm (trade name: trade name: manufactured by Nippon Seiki Seisakusho Co., Ltd.). 11 parts of Smartex PA2323, manufactured by Nippon A & L Co., Ltd., 3 parts of oxidized starch (trade name: Ace B, manufactured by Oji Cornstarch Co., Ltd.), 9 parts of 30% phosphoric acid aqueous solution, and lubricant (trade name: SN Coat 231SP) , Manufactured by San Nopco Co., Ltd.) was added to prepare a coating solution for an overcoat layer having a final solid content concentration of 65%.
Here, the thickness of the formed undercoat layer was 3.4 μm, the thickness of the formed overcoat layer was 12.0 μm, and the paper surface pH was 3.4. In addition, as in Example 4, "Cobb water absorption test of fine paper with an undercoat layer", "Water absorption test of topcoat layer", "High shear viscosity measurement of coating liquid for topcoat layer", "Blank paper" A gloss evaluation, a curl test, a droplet ejection test, a cockle test immediately after printing, and a density unevenness test were performed. However, regarding the “droplet ejection test”, the ink used was the same as that in Example 1, but the processing liquid was not used and image formation was performed by the following method. The results are shown in Table 1.

<Image formation>
A four-color single-pass image was formed using the apparatus shown in FIG. 2 using the cyan pigment ink C, magenta pigment ink M, yellow pigment ink Y, and black pigment ink K shown in Example 1 under the following conditions. .

--Ink drawing--
Head: 1,200 dpi / 20 inch width piezo full line head is arranged for four colors. Discharged droplet amount: 4-value recording of 0, 2.0, 3.5, 4.0 pL Driving frequency: 30 kHz (recording medium conveyance speed 635 mm / Sec)

-Drying (water drying, blow drying)-
Wind speed: 15m / s
Temperature: Heated from the back side of the recording surface of the recording medium with a contact type flat heater so that the surface temperature of the recording medium becomes 60 ° C. Air blowing area: 640 mm (drying time: about 1 second)

--Fixing--
Silicone rubber roller (hardness 50 °, nip width 5mm)
Roller temperature: 90 ° C
Pressure: 0.8 MPa

<Drip test evaluation>
The gray scale and the character image printed for evaluation were visually evaluated according to the following criteria.
[Standard]
AA: No image blur or intercolor mixture is observed, and “hawk” characters of 4 pt or less are resolved BB: Image blur, intercolor mixture is not observed, and 5 pt “hawk” characters are resolved CC: Image blur, color Inter-color mixture is often seen, and practicality is low DD: Image blur, inter-color mixture is severe, and practicality is extremely low

(Example 16)
<Preparation of coating liquid for first layer (undercoat layer)>
22.5% polyester urethane latex aqueous dispersion (glass transition temperature 49 ° C., minimum film-forming temperature 29 ° C .; trade name: Hydran AP-40F, manufactured by Dainippon Ink & Chemicals, Inc.) 100 parts water 6 0.8 part and 0.7 part of 10% Emulgen 109P (Kao Co., Ltd.) were added and thoroughly stirred and mixed, and then the liquid temperature of the resulting mixture was maintained at 15 to 25 ° C. to 21.0% An undercoat layer coating solution was obtained.

<Formation of undercoat layer>
Using a bar coater, apply the coating solution for the undercoat layer obtained on both sides of high-quality paper (trade name: Shiraoi, manufactured by Nippon Paper Industries Co., Ltd.) with a basis weight of 81.4 g / m ^2. Was adjusted to be 8.0 g / m ² one side at a time and dried at 70 ° C. for 3 minutes to form an undercoat layer. Here, the thickness of the formed undercoat layer was 7.1 μm. Furthermore, the soft calendar process shown below was performed with respect to the formed undercoat.

-Soft calendar processing-
Using a soft calender having a roll pair in which a metal roll and a resin roll are paired with respect to the high-quality paper having the undercoat layer formed on the surface, conditions for a surface temperature of the metal roll of 50 ° C. and a nip pressure of 50 kg / cm In soft calendar processing.

<Preparation of coating solution for second layer (overcoat layer)>
Kaolin (trade name: Kaoblite 90, manufactured by Shiraishi Calcium Co., Ltd.) 100 parts, 0.1N sodium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) 3.8 parts, 40% sodium polyacrylate (trade name) : Aron T-50, manufactured by Toagosei Co., Ltd.) 1.3 parts and 49.6 parts of water are mixed and dispersed using a non-bubbling kneader (trade name: NBK-2, manufactured by Nippon Seiki Seisakusho Co., Ltd.). 14 parts of a 50% styrene-butadiene copolymer latex (trade name: Nipol LX407K, manufactured by Nippon Zeon Co., Ltd.) with 65% kaolin dispersion and an average particle size of 130 nm, and a fatty acid calcium emulsion (trade name: Nopcoat C) -104-HS, manufactured by San Nopco) and 1 part of 1% carboxymethylcellulose sodium salt (trade name: Serogen EP, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 0% Emulgen 109P (manufactured by Kao Corporation) were added and 0.5 parts of an aqueous solution, the final solids concentration was prepared 59% of top coat layer coating solution. The high shear viscosity of the coating solution for topcoat layer was 50.2 mPa · s to 138.2 mPa · s.

<Formation of second layer (overcoat layer)>
Using the high-speed sheet-fed blade coater (device name: PM-9040M, manufactured by SMT Co., Ltd.) on both sides of the fine paper on which the undercoat layer has been formed, While adjusting so that the dry mass per hit was 20 g / m ² , each side was applied and dried at a temperature of 150 ° C. and a wind speed of 20 m / sec for 3 seconds to form an overcoat layer. At this time, the thickness of the formed overcoat layer per one side was 20.0 μm.

-Cobb water absorption test of fine paper with undercoat layer-
(1) In accordance with the water absorption test specified in JIS P8140, the coated surface of the fine paper on which the undercoat layer is formed has a Cobb water absorption (the amount of water permeation when contacting with water at 20 ° C. for 15 seconds g / m ² ) was measured.
(2) In accordance with the water absorption test specified in JIS P8140, the Cobb water absorption on the coated surface of the fine paper on which the undercoat layer was formed (the amount of water penetration when contacting with water at 20 ° C. for 2 minutes g / m ² ) was measured.
(3) In accordance with the water absorption test specified in JIS P8140, the coated surface of the high-quality paper on which the undercoat layer is formed has a Cobb water absorption (the amount of water penetration when contacting with diethylene glycol at 20 ° C. for 2 minutes g / m ² ) was measured.

-Water absorption test of topcoat layer-
Based on the Bristow method, measurements were made as follows.
(1) An overcoat layer cut to A6 size is placed on a measuring board, and after touching a head filled with a test solution, a scanning line (from inside to outside) as shown in FIG. It was measured. The measurement board changes the rotation speed (contact time between paper and ink) stepwise and rotates to obtain the relationship between the contact time and the liquid absorption amount (water absorption amount). Table 1 shows the amount of water absorption at a contact time of 0.5 seconds.
(2) Measurement was performed in the same manner except that the water of (1) was changed to pure water containing 30% by mass of diethylene glycol. Table 1 shows the liquid absorption amount at a contact time of 0.9 seconds.

-Method for measuring high shear viscosity of coating liquid for topcoat layer-
For the high shear viscosity, use a Hercules High Shear Viscometer (Hercules High Shear Viscometer: manufactured by Kumagai Riki Kogyo Co., Ltd.) and put an appropriate amount of the coating liquid for the topcoat layer in a cup with an inner diameter of 40 mm and an effective depth of 80.5 mm. Using Bob F (rotating body) having a diameter of 39.8 mm and an effective length of 25 mm (with a clearance of 0.1 mm from the cup), setting the sweep time to 10 seconds and setting the maximum rotation speed to 8800 rpm, the flow curve ([shear Measure (number of revolutions)]-[shear stress (torque)] curve), and apparent viscosity was determined from this.

-Glossy evaluation of white paper-
About the white background, in accordance with JIS Z8741 (1997), using a digital variable gloss meter (trade name: UGV-5D, manufactured by Suga Test Instruments Co., Ltd.), the glossiness at an incident angle of 75 ° and a light receiving angle of 75 ° Was measured and evaluated according to the following criteria.
[Standard]
AA: Glossiness was 50% or more BB: Glossiness was 35% or more and less than 50% CC: Glossiness was 20% or more and less than 35% DD: Glossiness was less than 20%

-Curl test-
For the recording medium on which the second layer (overcoat layer) was formed, water was applied to a test piece of 50 mm × 5 mm size in the MD and CD directions so that the water would be 10 g / m ^2, and the JAPAN TAPPI paper pulp test Method No. Based on the curl curvature measuring method prescribed | regulated to 15-2: 2000, the curl degree after 8 hours and 50% RH was measured in accordance with the following reference | standard at 23 degreeC.
[Standard]
AAA: curl degree of less than 5 AA: curl degree of 5 or more and less than 10 BB: curl degree of 10 or more and less than 20 CC: curl degree of 20 or more and less than 30 DD: curl degree of 30 or more

-Evaluation of cockle immediately after printing-
A 2 cm × 2 cm single-color 100% solid image was printed on the center of the postcard on a recording medium coated with a postcard-sized topcoat layer, and the maximum height of corrugation generated immediately after printing was measured with a laser displacement meter.
[Standard]
AA: 1 mm or more and less than 2 mm BB: 2 mm or more and less than 3 mm CC: 3 mm or more

-Evaluation of density unevenness-
A single-color 100% solid image printed for evaluation of cockle was visually evaluated according to the following criteria.
[Evaluation criteria]
AA: Solid image area density is uniform, white spots are not observed at all, and printing spots are not observed at all. BB: White spots, printing spots are somewhat, but there is no problem in practical use. CC: White spots, printing spots are seen a lot, practicality Low DD: White spots, severe print spots, extremely low utility

-Droplet test-
<Preparation of ink>

(1) Preparation of cyan pigment ink C (Preparation of pigment dispersion)
10 g of Cyanine Blue A-22 (CI.PB15: 3) manufactured by Dainichi Seika Co., Ltd., low molecular weight dispersant 2-1, 10.0 g, 4.0 g of glycerin, and 26 g of ion-exchanged water were mixed with stirring to obtain a dispersion. Was prepared. Next, using an ultrasonic irradiation device (SONICS Vibra-cell VC-750, tapered microchip: φ5 mm, Amplitude: 30%), the dispersion is intermittently irradiated with ultrasonic waves (irradiation 0.5 seconds, pause) (1.0 second) for 2 hours to further disperse the pigment to obtain a 20% by mass pigment dispersion. The low molecular weight dispersant 2-1 is represented by the following chemical formula.
Separately from the above, the compound shown below was weighed, stirred and mixed to prepare a mixed solution I.
Glycerin 5.0g
Diethylene glycol 10.0g
Olfin E1010 (Nissin Chemical Industry Co., Ltd.) 1.0g
Ion exchange water 11.0g
The mixture I was slowly added dropwise to 23.0 g of a stirred 44% SBR dispersion (polymer fine particles: 3% by mass of acrylic acid, Tg (glass transition temperature) 30 ° C.), and mixed by stirring. Prepared.
Further, 100 g of cyan pigment ink C (cyan ink) was prepared by stirring and mixing the mixed liquid II while slowly dropping into the 20% by mass pigment dispersion described above. Using the pH meter WM-50EG manufactured by Toa DKK Co., Ltd., the pH of the pigment ink C prepared in this way was measured, and the pH value was 8.5.

(2) Preparation of Magenta Pigment Ink M Instead of the pigment used in the preparation of Pigment Ink C, Chromatic Jet Magenta DMQ (PR-122) manufactured by Ciba Specialty Chemicals was used. Except for the pigment, a magenta pigment ink M (magenta ink) was prepared in the same manner as the preparation of the pigment ink C described above. When the pH of the pigment ink M thus prepared was measured with a pH meter WM-50EG manufactured by Toa DKK, the pH value was 8.5.

(3) Preparation of Yellow Pigment Ink Y In place of the pigment used in the preparation of Pigment Ink C, Irgalite Yellow GS (PY74) manufactured by Ciba Specialty Chemicals was used. Except for the pigment, yellow pigment ink Y (yellow ink) was prepared in the same manner as in the preparation of pigment ink C described above. When the pH of the pigment ink Y thus prepared was measured with a pH meter WM-50EG manufactured by Toa DKK, the pH value was 8.5.

(4) Preparation of Black Pigment Ink K Similar to the preparation of Pigment Ink C described above, except that the pigment dispersion used for the preparation of Pigment Ink C was a dispersion CAB-O-JETTM_200 (carbon black) manufactured by CABOT. The black pigment ink K (black ink) was prepared by the method described above. When the pH of the pigment ink K thus prepared was measured with a pH meter WM-50EG manufactured by Toa DKK Co., Ltd., the pH value was 8.5.

<Preparation of treatment liquid>
The treatment liquid was prepared by mixing the following materials.
・ Phosphoric acid 10g
・ Glycerin 20g
・ Diethylene glycol 10g
・ Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) 1g
・ Ion exchange water 59g
When the pH of the first treatment liquid thus prepared was measured with a pH meter WM-50EG manufactured by Toa DKK, the pH value was 1.0.

<Dropping method>
Using the cyan pigment ink C, magenta pigment ink M, yellow pigment ink Y, black pigment ink K, and processing liquid, four-color single-pass image formation was performed using the apparatus shown in FIG. 3 under the following conditions.

--- Treatment liquid head for precoat module-
Head: 600 dpi / 20 inch width piezo-full line head Discharge droplet volume: 0, 4.0 pL binary recording Drive frequency: 15 kHz (recording medium conveyance speed 635 mm / sec)
Drawing pattern: In the ink drawing process, a pattern that applies treatment liquid in advance to the position where at least one color ink is drawn is applied.

--- Water drying for precoat module (blow drying)-
Wind speed: 15m / s
Temperature: Heated from the back side of the recording surface of the recording medium with a contact type flat heater so that the surface temperature of the recording medium becomes 60 ° C.

--Ink drawing--
Head: 1,200 dpi / 20 inch width piezo full line head is arranged for 4 colors. Ejected droplet volume: 4-value recording of 0, 2.0, 3.5, 4.0 pL Driving frequency: 30 kHz (Recording medium transport speed 635 mm) / Sec)

-Drying (water drying, blow drying)-
Wind speed: 15m / s
Temperature: 60 ° C
Air blowing area: 640 mm (drying time 1 second)

--Fixing--
Silicone rubber roller (hardness 50 °, nip width 5mm)
Roller temperature: 90 ° C
Pressure: 0.8 MPa

<Evaluation method>
The gray scale and the character image printed for evaluation were visually evaluated according to the following criteria.
[Standard]
AA: Image blur and color mixing are not seen, and “hawk” characters of 4 pt or less are resolved.
BB: Image blur and color mixing between colors are not seen, and resolution up to 5 pt “hawk” characters.
CC: Image blurring and color mixing between colors are often observed and practicality is low.
DD: Image blurring and color mixing is severe, and practicality is extremely low.

(Example 17)
A recording medium was produced in the same manner as in Example 16 except that “Preparation of coating solution for undercoat layer” in Example 16 was changed as follows. Here, the thickness of the formed undercoat layer was 8.1 μm, and the thickness of the formed overcoat layer was 20.6 μm. In addition, as in Example 16, “Cobb water absorption test of fine paper having an undercoat layer”, “Water absorption test of topcoat layer”, “Measurement of high shear viscosity of coating liquid for topcoat layer”, “Blank paper” A gloss evaluation, a curl test, a droplet ejection test, a cockle test immediately after printing, and a density unevenness test were performed. The results are shown in Table 1. The high shear viscosity of the coating solution for topcoat layer was 50.2 mPa · s to 138.2 mPa · s.

<Preparation of coating liquid for first layer (undercoat layer)>
Kaolin (trade name: Kaoblite 90, manufactured by Shiraishi Calcium Co., Ltd.) 100 parts, 0.1N sodium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) 3.8 parts, 40% sodium polyacrylate (trade name) : Aron T-50, manufactured by Toagosei Co., Ltd.) 1.3 parts and 49.6 parts of water are mixed and dispersed using a non-bubbling kneader (trade name: NBK-2, manufactured by Nippon Seiki Seisakusho Co., Ltd.). A 65% kaolin dispersion was obtained. Next, 22.5% polyester urethane latex aqueous dispersion (glass transition temperature 49 ° C., minimum film-forming temperature 29 ° C .; trade name: Hydran AP-40F, manufactured by Dainippon Ink & Chemicals, Inc.) Add 5 parts of water and 7.0 parts of the obtained 65% kaolin dispersion and 0.8 part of 10% Emulgen 109P (Kao Co., Ltd.) and mix well. The liquid temperature was kept at 15 to 25 ° C. to obtain a 24.0% undercoat layer coating liquid.

(Example 18)
A recording medium was produced in the same manner as in Example 17 except that in the “formation of topcoat layer” in Example 17 except that the soft calendar process was performed as described below, the following changes were made. Here, the thickness of the formed undercoat layer was 8.1 μm, and the thickness of the formed overcoat layer was 19.1 μm. In addition, as in Example 16, “Cobb water absorption test of fine paper having an undercoat layer”, “Water absorption test of topcoat layer”, “Measurement of high shear viscosity of coating liquid for topcoat layer”, “Blank paper” A gloss evaluation, a curl test, a droplet ejection test, a cockle test immediately after printing, and a density unevenness test were performed. The results are shown in Table 1. The high shear viscosity of the coating solution for topcoat layer was 50.2 mPa · s to 138.2 mPa · s.

-Soft calendar processing-
Using a soft calender provided with a roll pair in which a metal roll and a resin roll are paired with respect to the high-quality paper having the undercoat layer formed on the surface, conditions of a surface temperature of the metal roll of 80 ° C. and a nip pressure of 50 kg / cm In soft calendar processing.

Example 19
A recording medium was produced in the same manner as in Example 18 except that the following changes were made in “Preparation of coating liquid for topcoat layer” and “Formation of topcoat layer” in Example 18. Here, the thickness of the formed undercoat layer was 8.1 μm, and the thickness of the formed overcoat layer was 20.9 μm. In addition, as in Example 16, “Cobb water absorption test of fine paper having an undercoat layer”, “Water absorption test of topcoat layer”, “Measurement of high shear viscosity of coating liquid for topcoat layer”, “Blank paper” A gloss evaluation, a curl test, a droplet ejection test, a cockle test immediately after printing, and a density unevenness test were performed. The results are shown in Table 1. The high shear viscosity of the coating solution for topcoat layer was 50.2 mPa · s to 138.2 mPa · s.

<Preparation of coating solution for second layer (overcoat layer)>
Kaolin (trade name: Kaoblite 90, manufactured by Shiraishi Calcium Co., Ltd.) 100 parts, 0.1N sodium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) 3.8 parts, 40% sodium polyacrylate (trade name: Aron T-50, manufactured by Toagosei Co., Ltd.) 1.3 parts and 49.6 parts of water were mixed and dispersed using a non-bubbling kneader (trade name: NBK-2, manufactured by Nippon Seiki Seisakusho Co., Ltd.) 14 parts of a 50% styrene-butadiene copolymer latex (trade name: Nipol LX407K, manufactured by Nippon Zeon Co., Ltd.) dispersed with 65% kaolin and having an average particle size of 130 nm, and fatty acid calcium emulsion (trade name: Nopcoat C) -104-HS, manufactured by San Nopco) and 1 part of 1% carboxymethylcellulose sodium salt (trade name: Serogen EP, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 0% Emulgen 109P (manufactured by Kao Corporation) were added and 0.5 parts of an aqueous solution, the final solids concentration was prepared 27% of top coat layer coating solution.

<Formation of second layer (overcoat layer)>
On both sides of the high-quality paper on which the undercoat layer is formed, the prepared coating solution for the overcoat layer is adjusted on each side using a bar coater while adjusting the dry mass per side to 20 g / m ^2. It was applied and dried at 70 ° C. for 5 minutes to form an overcoat layer.

(Example 20)
A recording medium was produced in the same manner as in Example 16 except that “Preparation of coating solution for undercoat layer” in Example 16 was changed as follows. Here, the thickness of the formed undercoat layer was 5.1 μm, and the thickness of the formed overcoat layer was 20.0 μm. In addition, as in Example 16, “Cobb water absorption test of fine paper having an undercoat layer”, “Water absorption test of topcoat layer”, “Measurement of high shear viscosity of coating liquid for topcoat layer”, “Blank paper” A gloss evaluation, a curl test, a droplet ejection test, a cockle test immediately after printing, and a density unevenness test were performed. The results are shown in Table 1. The high shear viscosity of the coating solution for topcoat layer was 50.2 mPa · s to 138.2 mPa · s.

<Preparation of coating liquid for first layer (undercoat layer)>
29.9% acrylic silicone latex aqueous dispersion (glass transition temperature 25 ° C., minimum film-forming temperature 20 ° C .; trade name: Aquabrid ASi-91, manufactured by Daicel Chemical Industries, Ltd.) 100 parts of water 41. 9 parts and 0.9 part of 10% Emulgen 109P (Kao Co., Ltd.) were added, and after sufficiently stirring and mixing, the liquid temperature of the resulting mixture was maintained at 15-25 ° C. to 21.0% An undercoat layer coating solution was obtained.

(Example 21)
A recording medium was produced in the same manner as in Example 16 except that “Preparation of coating solution for undercoat layer” in Example 16 was changed as follows. Here, the thickness of the formed undercoat layer was 7.4 μm, and the thickness of the formed overcoat layer was 20.0 μm. In addition, as in Example 16, “Cobb water absorption test of fine paper having an undercoat layer”, “Water absorption test of topcoat layer”, “Measurement of high shear viscosity of coating liquid for topcoat layer”, “Blank paper” A gloss evaluation, a curl test, a droplet ejection test, a cockle test immediately after printing, and a density unevenness test were performed. The results are shown in Table 1. The high shear viscosity of the coating solution for topcoat layer was 50.2 mPa · s to 138.2 mPa · s.

<Preparation of coating liquid for first layer (undercoat layer)>
Kaolin (trade name: Kaoblite 90, manufactured by Shiraishi Calcium Co., Ltd.) 100 parts, 0.1N sodium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) 3.8 parts, 40% sodium polyacrylate (trade name) : Aron T-50, manufactured by Toagosei Co., Ltd.) 1.3 parts and 49.6 parts of water are mixed and dispersed using a non-bubbling kneader (trade name: NBK-2, manufactured by Nippon Seiki Seisakusho Co., Ltd.). 65% kaolin dispersion was obtained. Then, 29.9% acrylic silicone latex aqueous dispersion (glass transition temperature 25 ° C., minimum film forming temperature 20 ° C .; trade name: Aquabrid ASi-91, manufactured by Daicel Chemical Industries, Ltd.) 7 parts and 13.9 parts of the obtained 65% kaolin dispersion and 1 part of 10% Emulgen 109P (Kao Co., Ltd.) were added and thoroughly stirred and mixed. By maintaining the temperature at 15 to 25 ° C., 32.0% of an undercoat layer coating solution was obtained.

(Example 22)
A recording medium was produced in the same manner as in Example 16 except that “Preparation of coating solution for undercoat layer” and “Formation of undercoat layer” in Example 16 were changed as follows. Here, the thickness of the formed undercoat layer was 6.2 μm, and the thickness of the formed overcoat layer was 20.4 μm. In addition, as in Example 16, “Cobb water absorption test of fine paper having an undercoat layer”, “Water absorption test of topcoat layer”, “Measurement of high shear viscosity of coating liquid for topcoat layer”, “Blank paper” Gloss evaluation, curl test, droplet ejection test, cuckling test immediately after printing, and density unevenness test were performed. The results are shown in Table 1. The high shear viscosity of the coating solution for topcoat layer was 50.2 mPa · s to 138.2 mPa · s.

<Preparation of coating liquid for first layer (undercoat layer)>
22.5% polyester urethane latex aqueous dispersion (glass transition temperature 49 ° C., minimum film-forming temperature 29 ° C .; trade name: Hydran AP-40F, manufactured by Dainippon Ink & Chemicals, Inc.) 100 parts water 4 4 parts and 35.7 parts of the obtained 63% kaolin slurry (trade name: Contour 1500, manufactured by Imerizu Minerals Japan) and 0.8 parts of 10% Emulgen 109P (Kao Corporation) In addition, after sufficiently stirring and mixing, the liquid temperature of the obtained mixed liquid was maintained at 15 to 25 ° C. to obtain a 32.0% undercoat layer coating liquid.

<Formation of undercoat layer>
The obtained coating liquid for undercoat layer was applied to both sides of high-quality paper (product name: Shiraoi, manufactured by Nippon Paper Industries Co., Ltd.) having a basis weight of 81.4 g / m ^2. 9040M, manufactured by SMT Co., Ltd.), applying one side at a time while adjusting the dry mass per side to 7.0 g / m ^2, and drying for 3 seconds at a temperature of 150 ° C. and a wind speed of 20 m / sec. Formed.

(Example 23)
A recording medium was produced in the same manner as in Example 16 except that “Preparation of coating solution for undercoat layer” and “Formation of undercoat layer” in Example 16 were changed as follows. Here, the thickness of the formed undercoat layer was 6.8 μm, and the thickness of the formed overcoat layer was 20.4 μm. In addition, as in Example 16, “Cobb water absorption test of fine paper having an undercoat layer”, “Water absorption test of topcoat layer”, “Measurement of high shear viscosity of coating liquid for topcoat layer”, “Blank paper” A gloss evaluation, a curl test, a droplet ejection test, a cockle test immediately after printing, and a density unevenness test were performed. The results are shown in Table 1. The high shear viscosity of the coating solution for topcoat layer was 50.2 mPa · s to 138.2 mPa · s.

<Preparation of coating liquid for first layer (undercoat layer)>
22.5% polyester urethane latex aqueous dispersion (glass transition temperature 49 ° C., minimum film forming temperature 29 ° C .; trade name: Hydran AP-40F, manufactured by Dainippon Ink & Chemicals, Inc.) 100 parts water 3 46.7 parts of the obtained 67.5% kaolin slurry (trade name: Astra Plate, manufactured by Imeris Minerals Japan) and 10 parts of Emulgen 109P (Kao Corporation) 0.8 parts The mixture was sufficiently stirred and mixed, and the liquid temperature of the obtained mixed liquid was kept at 15 to 25 ° C. to obtain a 31.0% undercoat layer coating liquid.

<Formation of undercoat layer>
The obtained coating liquid for undercoat layer was applied to both sides of high-quality paper (product name: Shiraoi, manufactured by Nippon Paper Industries Co., Ltd.) having a basis weight of 81.4 g / m ^2. 9040M, manufactured by SMT Co., Ltd.), applying one side at a time while adjusting the dry mass per side to 8.0 g / m ² , drying at a temperature of 150 ° C. and a wind speed of 20 m / sec for 3 seconds to undercoat A layer was formed.

(Comparative Example 1)
In the formation of the undercoat layer in Example 1, in place of the coated amount per one surface is adjusted to be 8.0 g / m ^2, except that coating amount was adjusted to be 6.0 g / m ² A recording medium was produced in the same manner as in Example 1. Here, the thickness of the formed undercoat layer was 5.8 μm, and the thickness of the formed overcoat layer was 9.8 μm. In addition, as in Example 1, “Cobb water absorption test of fine paper with an undercoat layer”, “Water absorption test of topcoat layer”, “High shear viscosity measurement of coating liquid for topcoat layer”, “Blank paper” A gloss evaluation, a curl test, a droplet ejection test, a cockle test immediately after printing, and a density unevenness test were performed. The results are shown in Table 1.

(Comparative Example 2)
In the preparation of the coating liquid for the top coat layer of Example 3, 60 parts of heavy calcium carbonate (trade name: Escalon # 2000, manufactured by Sankyo Seimitsu Co., Ltd.), kaolin (trade name: Milagros, manufactured by Engelhard Inc .: USA) 20 Instead of using 11 parts of styrene-butadiene copolymer latex (trade name: SMARTEX PA2323, manufactured by Nippon A & L Co., Ltd.) having an average particle size of 95 nm, heavy calcium carbonate (trade name: ESCALON # 2000, Sankyosei) 40 parts by powder), 40 parts by kaolin (trade name: Milagros, manufactured by Engelhard: USA), styrene-butadiene copolymer latex having an average particle size of 95 nm (trade name: Smartex PA2323, manufactured by Nippon A & L) A recording medium was produced in the same manner as in Example 3 except that 15 parts were used. Here, the thickness of the formed undercoat layer was 4.3 μm, and the thickness of the formed overcoat layer was 11.0 μm. In addition, as in Example 1, “Cobb water absorption test of fine paper with an undercoat layer”, “Water absorption test of topcoat layer”, “High shear viscosity measurement of coating liquid for topcoat layer”, “Blank paper” A gloss evaluation, a curl test, a droplet ejection test, a cockle test immediately after printing, and a density unevenness test were performed. The results are shown in Table 1.

(Comparative Example 3)
In the preparation of the coating liquid for the top coat layer of Example 3, 60 parts of heavy calcium carbonate (trade name: Escalon # 2000, manufactured by Sankyo Seimitsu Co., Ltd.), kaolin (trade name: Milagros, manufactured by Engelhard Inc .: USA) 20 Instead of using 11 parts of titanium oxide (Typaque R-780, manufactured by Ishihara Sangyo Co., Ltd.) and 11 parts of styrene-butadiene copolymer latex (trade name: SMARTEX PA2323, manufactured by Nippon A & L Co., Ltd.) having an average particle size of 95 nm. In addition, 70 parts of heavy calcium carbonate (trade name: Escalon # 2000, manufactured by Sankyo Seimitsu Co., Ltd.), 15 parts of kaolin (trade name: Milagros, manufactured by Engelhard Inc .: USA), titanium oxide (Taipaque R-780, Ishihara Sangyo) 15 parts, styrene-butadiene copolymer latex having an average particle size of 95 nm (trade name: SMARTEX PA23) 3, was replaced by Nippon A & L Inc.) 9 parts A recording medium was prepared in the same manner as in Example 3. Here, the thickness of the formed undercoat layer was 4.6 μm, and the thickness of the formed overcoat layer was 10.6 μm. In addition, as in Example 1, “Cobb water absorption test of fine paper with an undercoat layer”, “Water absorption test of topcoat layer”, “High shear viscosity measurement of coating liquid for topcoat layer”, “Blank paper” A gloss evaluation, a curl test, a droplet ejection test, a cockle test immediately after printing, and a density unevenness test were performed. The results are shown in Table 1.

(Comparative Example 4)
“Formation of undercoat layer” in Example 6 was changed without soft calender treatment, and in the preparation of a coating solution for topcoat layer, 60 parts of heavy calcium carbonate (trade name: Escalon # 2000, Sankyo Seimitsu Co., Ltd.) , 20 parts of kaolin (trade name: Milagros, manufactured by Engelhard: USA), 20 parts of titanium oxide (Typaque R-780, manufactured by Ishihara Sangyo Co., Ltd.), styrene-butadiene copolymer latex (trade name) having an average particle size of 95 nm : Instead of using 11 parts of SMARTEX PA2323, manufactured by Nippon A & L Co., Ltd., 40 parts of heavy calcium carbonate (trade name: Escalon # 2000, manufactured by Sankyo Seimitsu Co., Ltd.), kaolin (trade name: Milagros, manufactured by Engelhard) : USA) 50 parts, Titanium oxide (Taipaque R-780, manufactured by Ishihara Sangyo Co., Ltd.) 10 parts, an average particle size of 95 nm - butadiene copolymer latex (trade name: smart Tex PA2323, Nippon A & L Inc.) was replaced by 15 parts A recording medium was prepared in the same manner as in Example 6. Here, the thickness of the formed undercoat layer was 10.2 μm, and the thickness of the formed overcoat layer was 10.1 μm. In addition, as in Example 1, “Cobb water absorption test of fine paper with an undercoat layer”, “Water absorption test of topcoat layer”, “High shear viscosity measurement of coating liquid for topcoat layer”, “Blank paper” A gloss evaluation, a curl test, a droplet ejection test, a cockle test immediately after printing, and a density unevenness test were performed. The results are shown in Table 1.

(Comparative Example 5)
In “Preparation of coating solution for undercoat layer” in Example 6, 3.9 parts of 45% titanium dioxide dispersion was replaced with 11.7 parts, and in “Preparation of coating solution for topcoat layer”, heavy carbonate 60 parts of calcium (trade name: Escalon # 2000, Sankyo Seimitsu Co., Ltd.), 20 parts of kaolin (trade name: Milagros, Engelhard Inc .: USA), 20 parts of titanium oxide (Taipaque R-780, manufactured by Ishihara Sangyo Co., Ltd.) Instead of using 11 parts of styrene-butadiene copolymer latex (trade name: SMARTEX PA2323, manufactured by Nippon A & L Co., Ltd.) having an average particle size of 95 nm, heavy calcium carbonate (trade name: ESCALON # 2000, Sankyo Seimitsu) 70 parts, Kaolin (trade name: Milagros, Engelhard: USA) 10 parts, Titanium oxide (Taipeke R-780, manufactured by Ishihara Sangyo Co., Ltd.) 20 parts of an average particle diameter of 95nm styrene - butadiene copolymer latex (trade name: smart Tex PA2323, Nippon A & L Inc.) was replaced by 7 parts, to prepare a recording medium in the same manner as in Example 6. Here, the thickness of the formed undercoat layer was 9.6 μm, and the thickness of the formed overcoat layer was 9.8 μm. In addition, as in Example 1, “Cobb water absorption test of fine paper with an undercoat layer”, “Water absorption test of topcoat layer”, “High shear viscosity measurement of coating liquid for topcoat layer”, “Blank paper” A gloss evaluation, a curl test, a droplet ejection test, a cockle test immediately after printing, and a density unevenness test were performed. The results are shown in Table 1.

(Comparative Example 6)
In “Formation of undercoat layer” in Example 16, the same as in Example 16 except that the coating amount per side of the undercoat coating solution was changed from 8.0 g / m ² to 4.0 g / m ^2. Thus, a recording medium was produced. Here, the thickness of the formed undercoat layer was 3.8 μm, and the thickness of the formed overcoat layer was 18.9 μm. In addition, as in Example 16, “Cobb water absorption test of fine paper having an undercoat layer”, “Water absorption test of topcoat layer”, “Measurement of high shear viscosity of coating liquid for topcoat layer”, “Blank paper” A gloss evaluation, a curl test, a droplet ejection test, a cockle test immediately after printing, and a density unevenness test were performed. The results are shown in Table 1. In addition, the high shear viscosity of the coating liquid for top coat layers was 50.2 mPa · s to 138.2 mPa · s.

(Comparative Example 7)
In Example 17, “Formation of undercoat layer”, except that the coating amount per side of the undercoat coating solution was changed from 8.0 g / m ² to 4.0 g / m ^2. Thus, a recording medium was produced. Here, the thickness of the formed undercoat layer was 4.0 μm, and the thickness of the formed overcoat layer was 20.6 μm. In addition, as in Example 16, “Cobb water absorption test of fine paper having an undercoat layer”, “Water absorption test of topcoat layer”, “High shear viscosity measurement of coating solution for topcoat layer”, “Glossy white paper” "Evaluation", "Curl test", "Drip test", "Cuckle test immediately after printing", and "Density unevenness test" were performed. The results are shown in Table 1. In addition, the high shear viscosity of the coating liquid for top coat layers was 50.2 mPa · s to 138.2 mPa · s.

(Comparative Example 8)
In Comparative Example 7, a recording medium was produced in the same manner as in Comparative Example 7, except that the preparation of the coating solution for the topcoat layer was changed as described below, and the soft calendering process was performed. The thickness of the resulting undercoat layer was 4.0 μm, and the thickness of the formed overcoat layer was 5.1 μm. Further, as in Example 16, the “cobb water absorbency of the fine paper on which the undercoat layer was formed”. "Test", "Water absorption test of topcoat layer", "High shear viscosity measurement of coating liquid for topcoat layer", "Blank gloss evaluation", "Curl test", "Drip test", "Cuckle test immediately after printing" , And a “density unevenness test”. The results are shown in Table 1.

<Preparation of coating solution for second layer (overcoat layer)>
Kaolin (trade name: Kaoblite 90, manufactured by Shiraishi Calcium Co., Ltd.) 100 parts, 0.1N sodium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) 3.8 parts, 40% sodium polyacrylate (trade name: Aron T-50, manufactured by Toagosei Co., Ltd.) 1.3 parts and 49.6 parts of water were mixed and dispersed using a non-bubbling kneader (trade name: NBK-2, manufactured by Nippon Seiki Seisakusho Co., Ltd.) 14 parts of a 50% styrene-butadiene copolymer latex (trade name: Nipol LX407K, manufactured by Nippon Zeon Co., Ltd.) dispersed with 65% kaolin and having an average particle size of 130 nm, and a fatty acid calcium emulsion (trade name: Nopcoat C-) 104-HS (manufactured by San Nopco) was added to prepare a topcoat layer coating solution having a final solid content concentration of 59%. The high shear viscosity of the coating solution for the topcoat layer was 18.6 mPa · s to 90.2 mPa · s.

-Soft calendar processing-
Using a soft calender provided with a roll pair in which a metal roll and a resin roll are paired with respect to the high-quality paper having the undercoat layer formed on the surface, conditions of a surface temperature of the metal roll of 80 ° C. and a nip pressure of 50 kg / cm In soft calendar processing.

(Comparative Example 9)
A recording medium was produced in the same manner as in Comparative Example 8, except that “Preparation of coating liquid for topcoat layer” and “Formation of topcoat layer” in Comparative Example 8 were changed as follows. Here, the thickness of the formed undercoat layer was 4.0 μm, and the thickness of the formed overcoat layer was 19.6 μm. In addition, as in Example 16, “Cobb water absorption test of fine paper having an undercoat layer”, “Water absorption test of topcoat layer”, “High shear viscosity measurement of coating solution for topcoat layer”, “Glossy white paper” "Evaluation", "Curl test", "Drip test", "Cuckle test immediately after printing", and "Density unevenness test" were performed. The results are shown in Table 1.

<Preparation of coating solution for second layer (overcoat layer)>
Kaolin (trade name: Kaoblite 90, manufactured by Shiraishi Calcium Co., Ltd.) 100 parts, 0.1N sodium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) 3.8 parts, 40% sodium polyacrylate (trade name) : Aron T-50, manufactured by Toagosei Co., Ltd.) 1.3 parts and 49.6 parts of water are mixed and dispersed using a non-bubbling kneader (trade name: NBK-2, manufactured by Nippon Seiki Seisakusho Co., Ltd.). 14 parts of a 50% styrene-butadiene copolymer latex (trade name: Nipol LX407K, manufactured by Nippon Zeon Co., Ltd.) with 65% kaolin dispersion and an average particle size of 130 nm, and a fatty acid calcium emulsion (trade name: Nopcoat C) -104-HS (manufactured by San Nopco) and 1 part of 1% carboxymethylcellulose sodium salt (trade name: Serogen EP, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) 10% of Emulgen 109P was added and (manufactured by Kao Corp.) solution, 0.5 part of a final solid content concentration to prepare a 27% top coat layer coating solution. The high shear viscosity of the coating liquid for topcoat layer was 17.0 mPa · s to 50.9 mPa · s.

<Formation of second layer (overcoat layer)>
On both sides of the high-quality paper on which the undercoat layer is formed, the prepared coating solution for the overcoat layer is adjusted on each side using a bar coater while adjusting the dry mass per side to 20 g / m ^2. It was applied and dried at 70 ° C. for 5 minutes to form an overcoat layer.

* DEG: Diethylene glycol

From the results of Table 1-1 and Table 1-2, the Cobb absorbency at a contact time of 15 seconds according to the water absorption test defined in JIS P8140 of the base paper provided with the undercoat layer is 5.0 g / m ² or less. and water absorption amount at a contact time of 0.5 sec determined by the Bristow method of top coat layer is 2 mL / ^{m 2} or more 8 mL / ^{m 2} below examples 1 to 23, compared with Comparative examples 1 to 9, curl test, hitting The overall results for the drop test, the cockle test, and the density unevenness are excellent, and it can be seen that paper deformation and image bleeding are suppressed.

(Example 24)
<Preparation of coating liquid for first layer (undercoat layer)>
Kaolin (trade name: Kaoblite 90, manufactured by Shiraishi Calcium Co., Ltd.) 100 parts, 0.1N sodium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) 3.8 parts, 40% sodium polyacrylate (trade name: Aron T-50, manufactured by Toagosei Co., Ltd. (1.2 parts) and water (48.8 parts) were mixed and dispersed using a non-bubbling kneader (trade name: NBK-2, manufactured by Nippon Seiki Seisakusho Co., Ltd.). 65% kaolin dispersion was obtained. Next, 100 parts of 22.5% polyester urethane latex aqueous dispersion (glass transition temperature 49 ° C., minimum film-forming temperature 29 ° C .; trade name: Hydran AP-40F, manufactured by Dainippon Ink & Chemicals, Inc.) 5 parts and 6.9 parts of the obtained 65% kaolin dispersion and 0.8 part of 10% Emulgen 109P (manufactured by Kao Corporation) were added and thoroughly stirred and mixed. A temperature of 15 to 25 ° C. was maintained to prepare a 24.0% undercoat layer coating solution.

<Preparation of coating solution for second layer (overcoat layer)>
100 parts of kaolin (trade name: Kaoblite 90, manufactured by Shiraishi Calcium Co., Ltd.) and 1.2 parts of 40% sodium polyacrylate (trade name: Aron T-50, manufactured by Toagosei Co., Ltd.) are mixed in water. And 100 parts of 7% PVA245 aqueous solution (manufactured by Kuraray Co., Ltd.) and 3.7 parts of 10% aqueous solution of Emulgen 109P (manufactured by Kao Corporation) are added to give a final solid content concentration of 27%. An overcoat layer coating solution was prepared.

<Formation of first layer (undercoat layer)>
On both sides of a high-quality paper (trade name: Shiraoi, manufactured by Nippon Paper Industries Co., Ltd.) having a basis weight of 81.4 g / m ² , the obtained coating solution for the undercoat layer is applied to one side using an extrusion die coater. While adjusting the coating amount to 8.0 g / m ² , the coating was applied one side at a time and dried at a temperature of 85 ° C. and a wind speed of 15 m / sec for 1 minute to form an undercoat layer.
Furthermore, the soft calendar process shown below was performed with respect to the formed undercoat.

-Soft calendar processing-
Using a soft calender having a roll pair in which a metal roll and a resin roll are paired with respect to the high-quality paper having the undercoat layer formed on the surface, conditions for a surface temperature of the metal roll of 50 ° C. and a nip pressure of 50 kg / cm In soft calendar processing.

<Second layer formation>
On both sides of the fine paper on which the undercoat layer is formed, the prepared coating liquid for the second layer is applied on one side using an extrusion die coater so that the dry mass per side becomes 20 g / m ^2. It applied one by one and dried at a temperature of 70 ° C. and a wind speed of 10 m / sec for 1 minute to form a second layer.
Here, the thickness of the formed undercoat layer was 8.0 μm, and the thickness of the formed overcoat layer was 15.3 μm. The surface pH of the surface of the topcoat layer was 7.4.
Here, the surface pH can be measured by the A method (coating method) in the measurement of the film surface PH defined by the Japan Paper Pulp Technology Association (J.TAPPI), and corresponds to the A method, Kyoritsu Co., Ltd. This was carried out using a PH measurement set for paper “Type MPC” manufactured by RIKEN.

<Evaluation of recording medium>
For the recording medium obtained in Example 24, “Cobb water absorption test of fine paper with undercoat layer”, “Water absorption test of topcoat layer”, “Curl test”, “Drip test”, and “Print” The "immediate cockle test" was performed as follows. The results are shown in Table 2.

-Cobb water absorption test of fine paper with undercoat layer-
(1) In accordance with the water absorption test specified in JIS P8140, the coated surface of the fine paper on which the undercoat layer is formed has a Cobb water absorption (the amount of water permeation when contacting with water at 20 ° C. for 15 seconds g / m ² ) was measured.
(2) In accordance with the water absorption test specified in JIS P8140, the Cobb water absorption on the coated surface of the fine paper on which the undercoat layer was formed (the amount of water penetration when contacting with water at 20 ° C. for 2 minutes g / m ² ) was measured.
(3) In accordance with the water absorption test specified in JIS P8140, the coated surface of the fine paper on which the undercoat layer is formed has a Cobb value (the penetration amount of diethylene glycol when brought into contact with diethylene glycol at 20 ° C. for 2 minutes, g / m ² ) was measured.

-Water absorption test of topcoat layer-
(1) An overcoat layer cut to A6 size is placed on a measuring board, and after touching a head filled with a test solution, a scanning line (from inside to outside) as shown in FIG. It was measured. The measurement board changed the rotation speed (contact time between paper and ink) stepwise and rotated to obtain the relationship between the contact time and the liquid absorption amount (water absorption amount). Table 2 shows the water absorption amount at a contact time of 0.5 seconds.
(2) Measured in the same manner except that the water of (1) was changed to diethylene glycol. Table 2 shows the liquid absorption amount at a contact time of 0.9 seconds.

-Curl test-
For the recording medium on which the second layer (overcoat layer) was formed, water was applied to a test piece of 50 mm × 5 mm size in the MD and CD directions so that the water would be 10 g / m ^2, and the JAPAN TAPPI paper pulp test Method No. Based on the curl curvature measuring method prescribed | regulated to 15-2: 2000, the curl degree after 23 degreeC and 50% RH and 8 hours was measured according to the following reference | standard.
〔Evaluation criteria〕
AAA: curl degree of less than 5 AA: curl degree of 5 or more and less than 10 BB: curl degree of 10 or more and less than 20 CC: curl degree of 20 or more and less than 30 DD: curl degree of 30 or more

<PH adjustment of recording medium>
(Preparation of treatment liquid)
The treatment liquid was prepared by mixing the following materials.
・ Citric acid 15g
・ Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) ... 1g
・ Ion exchange water: 84g
When the pH of the treatment solution thus prepared was measured with a pH meter WM-50EG manufactured by Toa DKK Co., Ltd., the pH value was 1.5.
This treatment liquid was applied to a recording medium so as to be 5 g / m ² and dried at 60 ° C. and 15 m / s for 1 minute. The surface pH after the treatment was 3.6.
In subsequent tests, the pH was adjusted. This recording medium was used.
Here, the surface pH can be measured by the A method (coating method) in the measurement of the film surface PH defined by the Japan Paper Pulp Technology Association (J.TAPPI), and corresponds to the A method, Kyoritsu Co., Ltd. This was carried out using a PH measurement set for paper “Type MPC” manufactured by RIKEN.

-Evaluation of cockle immediately after printing-
A 2cm x 2cm monochromatic 100% solid image is printed in the center of a postcard on a pH-adjusted recording medium with a postcard-sized topcoat layer, and the maximum height of waviness generated immediately after printing is measured with a laser displacement meter. did.
[Evaluation criteria]
AA: 1 mm or more and less than 2 mm BB: 2 mm or more and less than 3 mm CC: 3 mm or more

-Droplet test-
<Preparation of ink>
(1) Preparation of cyan pigment ink C (Preparation of pigment dispersion)
Disperse by stirring and mixing 10 g of cyanine blue A-22 (CI.PB15: 3) manufactured by Dainichi Seika Co., Ltd., 10.0 g of low molecular weight dispersant 2-1, 4.0 g of glycerin, and 26 g of ion-exchanged water. A liquid was prepared. Subsequently, using an ultrasonic irradiation apparatus (manufactured by SONICS, Vibra-cell VC-750, taper microchip: diameter 5 mm, Amplitude: 30%), the dispersion is intermittently irradiated with ultrasonic waves (irradiation 0.5 seconds). Then, the pigment was further dispersed by irradiation for 2 hours at a rest of 1.0 second to obtain a 20% pigment dispersion. The low molecular weight dispersant 2-1 is represented by the following chemical formula.

Apart from the above, the following compounds were weighed and mixed by stirring to prepare a mixed solution I.
・ Glycerin ... 5.0g
・ Diethylene glycol: 10.0 g
・ Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) ... 1.0g
・ Ion exchange water: 11.0 g
This mixed liquid I was slowly added dropwise to 23.0 g of a stirred 44% SBR dispersion (polymer fine particles, 3% acrylic acid, Tg (glass transition temperature) 30 ° C.), and mixed by stirring to prepare mixed liquid II. did.
Further, 100 g of cyan pigment ink C (cyan ink) was prepared by stirring and mixing the mixed solution II while slowly dropping into the 20% pigment dispersion described above. When the pH of the pigment ink C thus prepared was measured using a pH meter WM-50EG manufactured by Toa DKK Corporation, the pH value was 8.5.

(2) Preparation of Magenta Pigment Ink M In place of the pigment used in the preparation of Pigment Ink C, Chromatic Jet Magenta DMQ (C.I. PR-122) manufactured by Ciba Specialty Chemicals was used. Except for the pigment, a magenta pigment ink M (magenta ink) was prepared in the same manner as the preparation of the pigment ink C described above. When the pH of the pigment ink M thus prepared was measured with a pH meter WM-50EG manufactured by Toa DKK Corporation, the pH value was 8.5.

(3) Preparation of Yellow Pigment Ink Y In place of the pigment used in the preparation of Pigment Ink C, Irgalite Yellow GS (C.I.PY74) manufactured by Ciba Specialty Chemicals was used. Except for the pigment, yellow pigment ink Y (yellow ink) was prepared in the same manner as in the preparation of pigment ink C described above. When the pH of the pigment ink Y thus prepared was measured with a pH meter WM-50EG manufactured by Toa DKK Corporation, the pH value was 8.5.

(4) Preparation of Black Pigment Ink K Similar to the preparation of Pigment Ink C described above except that the pigment dispersion used for the preparation of Pigment Ink C was a dispersion CAB-O-JETTM_200 (carbon black) manufactured by CABOT. By this method, a black pigment ink K (black ink) was prepared. When the pH of the pigment ink K thus prepared was measured with a pH meter WM-50EG manufactured by Toa DKK Corporation, the pH value was 8.5.

<Dropping method>
Using the cyan pigment ink C, magenta pigment ink M, yellow pigment ink Y, and black pigment ink K, a four-color single-pass image was formed using the apparatus shown in FIG. 2 under the following conditions.

--Ink drawing--
・ Head: 1,200 dpi / 20 inch width piezo full line head for 4 colors ・ Discharged droplet volume: 4-value recording of 0, 2.0, 3.5, 4.0 pL ・ Drive frequency: 30 kHz (of recording medium (Conveyance speed 635mm / sec)

-Drying (water drying, blow drying)-
・ Wind speed: 15m / s
・ Temperature: 60 ℃
-Air blowing area: 640 mm (drying time 1 second)

--Fixing--
・ Silicone rubber roller (hardness 50 °, nip width 5mm)
・ Roller temperature: 90 ℃
・ Pressure: 0.8MPa

<Evaluation method>
Visual evaluation was performed in accordance with the following criteria for line width variations and blurring in gray scale and thin line images (lines formed at 2 dot width) printed for evaluation.
[Evaluation criteria]
AA: Image blur and color mixture are not seen, fine line image is resolved BB: Image blur, color mix is not seen, and variation in fine line width is not a problem CC: Image blur, color gap Many color mixing is observed, fine line blurring is large and practicality is low. DD: Image blurring, intercolor mixing is severe, and fine lines cannot be resolved, so practicality is extremely low.

(Example 25)
A recording medium was produced in the same manner as in Example 24 except that “Preparation of coating solution for undercoat layer” and “Preparation of coating solution for topcoat layer” in Example 24 were changed as follows.
Here, the thickness of the formed undercoat layer was 6.2 μm, the thickness of the formed overcoat layer was 20.0 μm, and the surface pH was 7.2. Further, as in Example 24, “Cobb water absorption test of fine paper on which an undercoat layer was formed”, “Water absorption test of topcoat layer”, “Curl test”, “Drip test”, and “Just after printing” "Cuckle test" was conducted. The results are shown in Table 2.

<Preparation of coating liquid for first layer (undercoat layer)>
Kaolin (trade name: Kaoblite 90, manufactured by Shiraishi Calcium Co., Ltd.) 100 parts, 0.1N sodium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd.) 3.8 parts, 40% sodium polyacrylate (trade name: Aron) 1.3 parts of T-50, manufactured by Toagosei Co., Ltd.) and 49.6 parts of water are mixed and dispersed using a non-bubbling kneader (trade name: NBK-2, manufactured by Nippon Seiki Seisakusho Co., Ltd.) A 65% kaolin dispersion was obtained.
Subsequently, 29.9% acrylic silicone latex aqueous dispersion (glass transition temperature 25 ° C., minimum film-forming temperature 20 ° C .; trade name: Aquabrid ASi-91, manufactured by Daicel Chemical Industries, Ltd.) 100 parts of water 7 And 13.9 parts of the obtained 65% kaolin dispersion and 1 part of 10% Emulgen 109P (manufactured by Kao Corporation) were thoroughly stirred and mixed, and then the liquid temperature of the resulting mixture was changed to 15 A coating solution for undercoat layer of 32.0% was obtained by maintaining the temperature at 25 ° C to 25 ° C.

<Preparation of coating solution for second layer (overcoat layer)>
In the preparation of the topcoat layer coating solution in Example 24, instead of using kaolin (trade name: Kaoblite 90, manufactured by Shiraishi Calcium Co., Ltd.), titanium dioxide (trade name: Tycop R-780, Ishihara Sangyo Co., Ltd.) A coating solution for topcoat layer was prepared in the same manner as in Example 24 except that (manufactured) was used.

(Example 26)
In the preparation of the coating solution for the topcoat layer in Example 24, instead of using 100 parts of kaolin (trade name: Kaoblite 90, manufactured by Shiroishi Calcium Co., Ltd.), titanium dioxide (trade name: Typaque R-780, Ishihara Sangyo) 30 parts, Kaolin (trade name: Kaoblite 90, manufactured by Shiraishi Calcium Co., Ltd.) and 43% sodium polyacrylate (trade name: Aron T-50, manufactured by Toagosei Co., Ltd.) 5 parts are mixed and dispersed in water, and 11 parts of styrene-butadiene copolymer latex (trade name: SMARTEX PA2323, manufactured by Nippon A & L Co.) having an average particle size of 95 nm and oxidized starch (trade name: ACE B) 3 parts of Oji Cornstarch Co., Ltd.) and 1 part of lubricant (trade name: SN Coat 231SP, San Nopco Co., Ltd.) Te, except that the final solid content concentration to prepare a 65% of the top coat layer coating solution, A recording medium was prepared in the same manner as in Example 24.
Here, the thickness of the formed undercoat layer was 8.1 μm, the thickness of the formed overcoat layer was 20.6 μm, and the surface pH was 7.4. Further, as in Example 24, “Cobb water absorption test of fine paper on which an undercoat layer was formed”, “Water absorption test of topcoat layer”, “Curl test”, “Drip ejection test (described in Example 24) The evaluation was performed in the same manner as in the above method), and “cuckle test immediately after printing”. The results are shown in Table 2.

(Example 27)
In the preparation of the coating solution for the topcoat layer in Example 26, the same procedure as in Example 26 was performed except that 100 parts of kaolin (trade name: Kaoblite 90, manufactured by Shiraishi Calcium Co., Ltd.) was used instead of titanium dioxide and kaolin. Thus, a recording medium was produced.
Here, the thickness of the formed undercoat layer was 8.1 μm, the thickness of the formed overcoat layer was 19.8 μm, and the surface pH was 7.6. Further, as in Example 24, “Cobb water absorption test of fine paper on which an undercoat layer was formed”, “Water absorption test of topcoat layer”, “Curl test”, “Drip ejection test (described in Example 24) Evaluation was performed in the same manner as the method) and “cuckle test immediately after printing”. The results are shown in Table 2.

(Example 28)
A recording medium was produced in the same manner as in Example 25 except that “Preparation of coating liquid for topcoat layer” in Example 25 was changed in the same manner as in Example 24.
Here, the thickness of the formed undercoat layer was 6.2 μm, the thickness of the formed overcoat layer was 20.0 μm, and the surface pH was 7.2. Further, except that “pH adjustment of the recording medium” was not performed and the “droplet deposition method” in the “droplet ejection test” was changed to the following, “the quality of the high quality paper on which the undercoat layer was formed” was changed in the same manner as in Example 24. "Cobb water absorption test", "Water absorption test of topcoat layer", "Curl test", "Drip test (evaluated by the method shown below)" and "Cuckle test immediately after printing" were performed. The results are shown in Table 2.

<Dropping method>
4 using the apparatus shown in FIG. 3 under the following conditions using the same cyan pigment ink C, magenta pigment ink M, yellow pigment ink Y, black pigment ink K, and treatment liquid as those prepared in Example 24. Color single pass imaging was performed.

<Preparation of treatment liquid>
The treatment liquid was prepared by mixing the following materials.
・ Citric acid 15g
・ Glycerin 20g
・ Diethylene glycol ... 10g
・ Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) ... 1g
・ Ion exchange water: 54g
When the pH of the treatment solution thus prepared was measured with a pH meter WM-50EG manufactured by Toa DKK, the pH value was 1.6.

--- Treatment liquid head for precoat module-
・ Head: 600 dpi / 20 inch width piezo full line head ・ Discharge droplet volume: binary recording of 0, 4.0 pL ・ Drive frequency: 15 kHz (recording medium conveyance speed 635 mm / sec)
Drawing pattern: In the ink drawing process, a pattern in which a treatment liquid is applied in advance to a position where at least one color ink is drawn is applied.

--- Water drying for precoat module (blow drying)-
・ Wind speed: 15m / s
-Temperature: Heated from the back of the recording surface of the recording medium with a contact type flat heater so that the surface temperature of the recording medium is 60 ° C.

--Ink drawing--
・ Head: 1,200 dpi / 20 inch width piezo full line head for 4 colors ・ Discharged droplet volume: 4-value recording of 0, 2.0, 3.5, 4.0 pL ・ Drive frequency: 30 kHz (of recording medium (Conveyance speed 635mm / sec)

-Drying (water drying, blow drying)-
・ Wind speed: 15m / s
・ Temperature: 60 ℃
-Air blowing area: 640 mm (drying time 1 second)

--Fixing--
・ Silicone rubber roller (hardness 50 °, nip width 5mm)
・ Roller temperature: 90 ℃
・ Pressure: 0.8MPa

(Example 29)
In Example 25, a recording medium was produced in the same manner as in Example 25 except that “pH adjustment of the recording medium” was not performed. Here, the thickness of the formed undercoat layer was 6.2 μm, the thickness of the formed overcoat layer was 20.0 μm, and the surface pH was 7.0. Further, as in Example 24, “Cobb water absorption test of fine paper on which an undercoat layer was formed”, “Water absorption test of topcoat layer”, “Curl test”, “Drip test”, and “Just after printing” "Cuckle test" was conducted. The results are shown in Table 2.

(Comparative Example 10)
<Preparation of coating liquid for first layer (undercoat layer)>
10 parts of sodium tetraborate decahydrate (1.62 parts in terms of H ₃ BO ₃ ) are dissolved in 350 parts of water, and 100 parts of wet synthetic silica (manufactured by Tokuyama Corporation, fan seal X-37B) is dissolved therein. After the addition, dispersion was performed using a non-bubbling kneader (trade name: NBK-2, manufactured by Nippon Seiki Seisakusho Co., Ltd.). Thereafter, 83.3 parts of styrene-butadiene (SBR) latex having a solid content of 48% (manufactured by JSR Corporation, 0623N) (40 parts as non-volatile content) was added and mixed, and the following coating solution for topcoat layer was added. The pH was adjusted with aluminum hydroxide so that the surface pH after application of the overcoat layer was 8.2 to prepare an undercoat layer coating solution.

<Preparation of coating solution for second layer (overcoat layer)>
Acetic acid 0.2 part is mixed with 74.8 parts of water, 25 parts of alumina hydrate having a pseudo boehmite structure (Dissal HP14, manufactured by Sasol Co.) is added and dispersed in water, saponification degree 88 mol%, 4% 20 parts of a 10% aqueous solution of polyvinyl alcohol (PVA235, manufactured by Kuraray Co., Ltd.) having a viscosity of 95 mPa · s at 25 ° C. was added to obtain a coating solution for topcoat layer.

<Formation of first layer (undercoat layer)>
On both sides of a high-quality paper (trade name: Shiraoi, manufactured by Nippon Paper Industries Co., Ltd.) having a basis weight of 81.4 g / m ² , the obtained coating solution for the undercoat layer is applied to one side using an extrusion die coater. While adjusting the coating amount to be 10 g / m ² , the coating was applied one side at a time and dried at a temperature of 85 ° C. and a wind speed of 15 m / sec for 1 minute to form an undercoat layer.
Furthermore, the soft calendar process shown below was performed with respect to the formed undercoat.

-Soft calendar processing-
Using a soft calender having a roll pair in which a metal roll and a resin roll are paired with respect to the high-quality paper having the undercoat layer formed on the surface, conditions for a surface temperature of the metal roll of 50 ° C. and a nip pressure of 50 kg / cm In soft calendar processing.

<Second layer formation>
On both sides of the fine paper on which the undercoat layer is formed, the prepared second layer coating solution is applied on one side using an extrusion die coater so that the dry mass per side becomes 10 g / m ^2. It applied one by one, and dried for 1 minute at a temperature of 70 ° C. and a wind speed of 10 m / sec to form a second layer.
Here, the thickness of the formed undercoat layer was 9.6 μm, and the thickness of the formed overcoat layer was 9.8 μm.

  Further, the pH was adjusted using acetic acid so that the surface pH was 3.5, and, as in Example 1, “Cobb water absorption test of fine paper on which undercoat layer was formed”, “Water absorption of topcoat layer” "Test", "Curl test", "Drip test", and "Cuckle test immediately after printing" were performed. The results are shown in Table 2.

(Comparative Example 11)
Except that “Preparation of coating solution for undercoat layer” and “Preparation of coating solution for topcoat layer” in Example 24 were changed as follows, and that soft calender treatment was not performed after coating of undercoat layer Produced a recording medium in the same manner as in Example 24.
Here, the thickness of the formed undercoat layer was 7.6 μm, the thickness of the formed overcoat layer was 20.0 μm, and the surface pH was 9.2. Further, as in Example 24, “Cobb water absorption test of fine paper on which an undercoat layer was formed”, “Water absorption test of topcoat layer”, “Curl test”, “Drip test”, and “Just after printing” "Cuckle test" was conducted. The results are shown in Table 2.

<Preparation of coating liquid for first layer (undercoat layer)>
100 parts of titanium dioxide (trade name: Taipei R-780, manufactured by Ishihara Sangyo Co., Ltd.), 1.2 parts of Na salt of 25% special polycarboxylic acid type polymer (trade name: Demol EP, manufactured by Kao Corporation), And 121.7 parts of water were mixed and dispersed using a non-bubbling kneader (trade name: NBK-2, manufactured by Nippon Seiki Seisakusho Co., Ltd.) to obtain a 45% titanium dioxide dispersion.
Next, 100 parts of water is obtained in 100 parts of 35% acrylic latex aqueous dispersion (glass transition temperature 60 ° C., minimum film-forming temperature 50 ° C .; trade name: Aquabrid 4635, manufactured by Daicel Chemical Industries, Ltd.). Then, 3.9 parts of 45% kaolin dispersion liquid was added and sufficiently stirred and mixed, and then the liquid temperature of the obtained liquid mixture was maintained at 15 to 25 ° C. to obtain a 18.0% undercoat layer coating liquid. Obtained.

<Preparation of coating solution for second layer (overcoat layer)>
Mix 100 parts of calcium bicarbonate (trade name: Escalon # 2000, Sankyo Flour Milling Co., Ltd.) and 1.2 parts of 40% sodium polyacrylate (trade name: Aron T-50, manufactured by Toagosei Co., Ltd.) Then, 100 parts of a 7% PVA245 aqueous solution (manufactured by Kuraray Co., Ltd.) and 3.7 parts of a 10% aqueous solution of Emulgen 109P (manufactured by Kao Corporation) are added to obtain a final solid content concentration. A 27% overcoat layer coating solution was prepared.

(Comparative Example 12)
A recording medium was produced in the same manner as in Comparative Example 11. Here, the thickness of the formed undercoat layer was 7.6 μm, the thickness of the formed overcoat layer was 20.0 μm, and the surface pH was 9.2. Further, except that “pH adjustment of the recording medium” was not performed and the “droplet deposition method” in the “droplet ejection test” was changed to the following, “the quality of the high quality paper on which the undercoat layer was formed” was changed in the same manner as in Example 24. "Cobb water absorption test", "Water absorption test of topcoat layer", "Curl test", "Drip test (evaluated by the method shown below)" and "Cuckle test immediately after printing" were performed. The results are shown in Table 2.

<Dropping method>
Using the apparatus shown in FIG. 3 under the following conditions using the same cyan pigment ink C, magenta pigment ink M, yellow pigment ink Y, black pigment ink K, and treatment liquid as those prepared in Example 24. Four-color single-pass image formation was performed.

<Preparation of treatment liquid>
The treatment liquid was prepared by mixing the following materials.
・ Citric acid 15g
・ Glycerin 20g
・ Diethylene glycol ... 10g
・ Orphine E1010 (manufactured by Nissin Chemical Industry Co., Ltd.) ... 1g
・ Ion exchange water: 54g
When the pH of the treatment solution thus prepared was measured with a pH meter WM-50EG manufactured by Toa DKK, the pH value was 1.5.

--- Treatment liquid head for precoat module-
・ Head: 600 dpi / 20 inch width piezo full line head ・ Discharge droplet volume: binary recording of 0, 4.0 pL ・ Drive frequency: 15 kHz (recording medium conveyance speed 635 mm / sec)
Drawing pattern: In the ink drawing process, a pattern in which a treatment liquid is applied in advance to a position where at least one color ink is drawn is applied.

--- Water drying for precoat module (blow drying)-
・ Wind speed: 15m / s
・ Temperature: Heated from the back of the recording surface of the recording medium so that the surface temperature of the recording medium becomes 60 ° C. ・ Blowing area: 450 mm (drying time 0.7 seconds)

--Ink drawing--
・ Head: 1,200 dpi / 20 inch width piezo full line head for 4 colors ・ Discharged droplet volume: 4-value recording of 0, 2.0, 3.5, 4.0 pL ・ Drive frequency: 30 kHz (of recording medium (Conveyance speed 635mm / sec)

-Drying (water drying, blow drying)-
・ Wind speed: 15m / s
・ Temperature: 60 ℃
-Air blowing area: 640 mm (drying time 1 second)

--Fixing--
・ Silicone rubber roller (hardness 50 °, nip width 5mm)
・ Roller temperature: 90 ℃
・ Pressure: 0.8MPa

* DEG: Diethylene glycol

FIG. 1 is an explanatory diagram of a recording medium of the present invention. FIG. 2 is an explanatory diagram of an ink jet recording method using the recording medium of the present invention (part 1). FIG. 3 is an explanatory diagram of an ink jet recording method using the recording medium of the present invention (part 2). FIG. 4 is a diagram for explaining a scanning line of a head filled with a test solution in the Bristow method. FIG. 5 is an explanatory diagram of a conventional recording medium.

Explanation of symbols

11 Quality Paper 12 Solvent Blocking Layer 13 Ink Absorbing Layer 21 Base Paper 22 Solvent Absorbing Layer 100 Recording Medium 200 Inkjet Paper

Claims (18)

In a recording medium formed by sequentially laminating a base paper, a first layer containing a binder, and a second layer containing a white pigment, the base paper provided with the first layer is water-absorbing as defined in JIS P8140. Cobb water absorption degree during a contact time 15 seconds by the time the test is at 5.0 g / ^{m 2} or less, and said second layer, water absorption amount at a contact time of 0.5 sec determined by the Bristow method is 2 mL / ^{m 2} or more 8mL / M ² or less. 2. The recording medium according to claim 1, wherein the base paper provided with the first layer has a Cobb water absorption of 2.0 g / m ² or less at a contact time of 2 minutes according to a water absorption test specified in JIS P8140. The base paper provided with the first layer has a Cobb value of not more than 5.0 g / m ^{2 with} a contact time of 2 minutes determined using diethylene glycol based on a water absorption test specified in JIS P8140, and The second layer has a water absorption amount of 1 mL / m ² or more and 6 mL / m ² or less in a contact time of 0.9 seconds determined using pure water containing 30% by mass of diethylene glycol by the Bristow method. A recording medium according to any one of the above.   The recording medium according to any one of claims 1 to 3, wherein the layer surface pH of the second layer is less than 8.0 before pH adjustment.   The recording medium according to any one of claims 1 to 4, wherein the white pigment comprises only a white pigment having a pH of less than 8.0 according to a pH value test method (normal temperature extraction method) defined in JIS K5101.   The white pigment has a pH of less than 6.0 after adding 0.1 mL of 1 mol / L hydrochloric acid to 10 g of a measurement solution of a pH value test method (normal temperature extraction method) defined in JIS K5101. To 5. The recording medium according to any one of 5 to 5.   The recording medium according to any one of claims 1 to 6, wherein the layer surface pH of the second layer is 5.5 or less after pH adjustment.   The recording medium according to claim 1, wherein the binder in the first layer contains a thermoplastic resin.   The recording medium according to claim 8, wherein the thermoplastic resin is at least one selected from polyester urethane latex and acrylic silicone latex.   The recording medium according to claim 1, wherein the first layer further contains a layered inorganic compound.   The recording medium according to claim 1, wherein the first layer further contains a white pigment.   The recording medium according to claim 11, wherein the white pigment is kaolin.   The recording medium according to claim 12, wherein kaolin has an aspect ratio of 30 or more.   14. The method according to claim 1, comprising: a first forming step of forming a first layer on the base paper; and a second forming step of forming a second layer on the first layer. A method for producing a recording medium, wherein in the first forming step, the thermoplastic resin fine particles provided on the surface of the base paper are heat-treated in a temperature range equal to or higher than a minimum film-forming temperature of the thermoplastic resin fine particles. A method for manufacturing a recording medium. The coating liquid for forming the second layer has a shear rate D (= S / (t × 60 ×) defined by the coating rate S (m / min) and the coating layer thickness t (μm). The method for producing a recording medium according to claim 14, wherein in the case where 10 ⁻⁶ )) is in the range of 10 ^{3 to} 10 ⁶ (s ⁻¹ ), the high shear viscosity is 20 mPa · s to 150 mPa · s.   16. The method for manufacturing a recording medium according to claim 14, wherein in the second forming step, a coating liquid for forming the second layer is applied by a blade coating method.   An ink drawing step of drawing ink on the recording medium according to any one of claims 1 to 13 in accordance with predetermined image data, and a dry removal step of drying and removing the ink solvent in the ink drawn recording medium. An ink jet recording method comprising:   A processing liquid supply step for supplying a processing liquid containing an acidic substance to the recording medium according to claim 1, and an ink corresponding to predetermined image data for the recording medium supplied with the processing liquid. An ink jet recording method comprising: an ink drawing step of drawing, and a drying removal step of drying and removing an ink solvent in the ink-drawn recording medium.