JP2010030216A - Recording medium and its manufacturing method as well as inkjet recording method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a recording medium which enables inhibition of the generation of a curl, an image feathering phenomenon and intercolor color mixture in an image recording process, as well as forming of a high-quality image, with an effect to make ink stripping hardly occur. <P>SOLUTION: This recording medium has a sheet of stencil paper 11, a first layer 12 including a binder and a second layer 13 containing kaolin and a polyvinyl alcohol with the degree of polymerization of not less than 1,500 to not more than 8,000 and a polyvinyl alcohol with the degree of polymerization of not less than 100 to less than 1,500, piled up in that order. In addition, the cup water absorbing capacity in the surface of the first layer for the contact time of 120 sec by a water absorbing capacity test in compliance with JIS P8140, is not more than 2.0 g/m<SP>2</SP>Further, the absorption volume of a diethylene glycol in the surface of the second layer for the contact time of 30 sec., is not less than 2 mL/m<SP>2</SP>to not more than 8 mL/m<SP>2</SP>. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

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

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

  In general, the ink contains 50% to 90% 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, and water is often used particularly from the viewpoint of environmental suitability. Further, a high boiling point solvent such as glycerin is generally used as the ink solvent 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, when a large amount of ink solvent is present in the ink-drawn recording medium, image bleeding and color mixing between colors are likely to occur due to the large amount of ink solvent. For this reason, an ink jet dedicated paper (see FIG. 4) having a solvent absorbing layer (ink receiving layer) of about 20 to 30 μm that absorbs the ink solvent on the surface is used as a recording medium, and image bleeding and color mixing between colors occur. Is suppressed.

  Further, in the case of water-based ink using water as the ink solvent, paper permeation such as curling occurs when water penetrates into the base paper during recording. However, as shown in FIG. When the solvent absorption layer 22 is provided on the top, water can be prevented from penetrating into the base paper, and paper deformation can be suppressed.

  In particular, when a graphical image with a high image density or image area ratio is to be formed, 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, laminated paper) covered with a resin layer using polyolefin or the like is generally used (for example, see Patent Documents 1 and 2).

  However, the ink jet technology is not only applied in the fields of office printers, home printers, etc., 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. However, if the solvent absorption layer constituting 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 limited in terms of surface gloss, texture, stiffness, etc., on the recording medium.

  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, an inkjet recording material containing two or more kinds of PVA having different degrees of polymerization containing vapor phase silica or titanium oxide as fine particles and a method for producing the same are disclosed (for example, see Patent Document 3).
JP 2005-238829 A JP 2005-96285 A JP 2001-150805 A

  However, the recording medium described in the above-mentioned patent document cannot sufficiently suppress paper deformation such as curling, coating unevenness (coating property, coating surface shape), and the like. Further, in the printing method described in the above-mentioned patent document, the actual situation is that image bleeding, color mixing between colors, ink peeling and the like cannot be sufficiently suppressed.

  The present invention has been made in view of the above, and prevents the occurrence of curling accompanying image recording, image bleeding and color mixing between colors, and prevents the image from peeling off, thereby forming a high-quality image. It is an object of the present invention to provide a recording medium and a method for manufacturing the recording medium, and an ink jet recording method capable of forming a high-quality image at a low cost and at a high speed while suppressing image bleeding and color mixing between colors.

<1>
A base paper, a first layer containing a binder, a second layer containing kaolin, a polyvinyl alcohol having a polymerization degree of 1500 or more and 8000 or less and a polyvinyl alcohol having a polymerization degree of 100 or more and less than 1500 are sequentially laminated, The Cobb water absorption at a contact time of 120 seconds according to JIS P8140 on the surface of the first layer is 2.0 g / m ² or less, and the surface of the second layer is diethylene glycol having a contact time of 30 seconds. A recording medium having an absorption capacity of 2 mL / m ² or more and 8 mL / m ² or less.
<2>
The recording medium according to <1>, wherein the second layer further contains calcined kaolin.
<3>
The recording medium according to <1> or <2>, wherein the polymerization degree of the polyvinyl alcohol having a polymerization degree of 1500 or more and 8000 or less is 3000 or more and 8000 or less.
<4>
The recording medium according to any one of <1> to <3>, wherein the second layer further contains a styrene-butadiene copolymer rubber.
<5>
The recording medium according to any one of <1> to <4>, wherein the binder of the first layer is a latex of a thermoplastic resin.

<6>
A first layer forming step of forming a first layer by applying a film-forming solution containing a binder on a base paper, and after adding a pigment dispersion containing kaolin to polyvinyl alcohol having a polymerization degree of 100 or more and less than 1500 And a second layer forming step of forming a second layer by applying a film-forming solution obtained by adding polyvinyl alcohol having a polymerization degree of 1500 or more and 8000 or less onto the first layer. Manufacturing method.
<7>
The method for producing a recording medium according to <6>, wherein in the second layer forming step, the film forming liquid of the second layer is curtain-coated.

<8>
An ink drawing process in which ink is applied to the recording medium according to any one of the above <1> to <5> and ink is drawn according to predetermined image data, and ink on the recording medium on which ink is drawn And a drying removal step of drying and removing the solvent.
<9>
Using the recording medium according to any one of <1> to <5> above, a treatment liquid supply step of supplying a treatment liquid containing an acidic substance to the recording medium, and applying ink to the recording medium in advance. The ink jet recording method according to <8>, further comprising: an ink drawing step of drawing ink according to the defined image data; and a drying removal step of drying and removing the ink solvent in the recording medium on which the ink has been drawn.
<10>
The inkjet recording method according to <9>, wherein the acidic substance is a divalent or higher acid.

  According to the present invention, the recording medium capable of preventing the occurrence of curling accompanying image recording, image bleeding, and color mixing between colors and preventing the ink from peeling off and forming a high-quality image, and the production thereof. It is possible to provide a method and an ink jet recording method in which image bleeding and color mixing between colors are suppressed and a high-quality image can be formed at low cost and at high speed.

  Hereinafter, the recording medium of the present invention, the manufacturing method thereof, and the ink jet recording method using the recording medium will be described in detail.

<Recording medium>
The recording medium of the present invention comprises a base paper and a first layer and a second layer provided in this order from the base paper side, and if necessary, further appropriately selected other layers are provided. Can be configured. The recording medium of the present invention includes, for example, 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, like a recording medium 100 shown in FIG. A coating layer 13 as a second layer formed on the blocking layer 12 may be provided. The recording medium may be either sheet paper or roll paper.

(Base paper)
There is no restriction | limiting in particular as a 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 high level at the same time. In addition, softwood bleached kraft pulp (NBKP), hardwood sulfite pulp (LBSP), and the like can be used.

  A beater or refiner can be used for beating the pulp. In the pulp slurry obtained after beating the pulp (hereinafter sometimes referred to as “pulp paper material”), various additives such as a filler, a dry paper strength enhancer, a sizing agent, and wet paper strength are used as necessary. An 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 to a pulp paper stock 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, polyamide polyamine epichlorohydrin, and the like.
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.

  As thickness of a base paper, 30-500 micrometers is preferable, More preferably, it is 50-300 micrometers, More preferably, it is 70-200 micrometers.

(First layer)
The recording medium of the present invention has a first layer on the base paper. By providing the first layer, the penetration of the ink solvent into the base paper is suppressed.
For example, as a paper having a solvent blocking layer, a paper having a coating layer mainly composed of a polyethylene resin as a main component on the surface of the base paper, specifically, a paper provided with water resistance by providing the above-described solvent blocking layer. In this case, the effect of preventing water penetration is almost perfect, but the texture as paper is not always satisfactory, whereas the recording medium of the present invention is excellent in texture because the first layer is provided. .
The first layer contains at least a binder, and the surface of the first layer has a Cobb water absorption of 2.0 g at a contact time of 120 seconds according to a water absorption test according to JIS P8140 on the surface of the first layer. / M ² or less. If it is this range, there will be no restriction | limiting in particular, As a 1st layer, it can select suitably from well-known things according to the objective.
A 1st layer can be comprised using other components, such as a white pigment, a hardener, and a layered inorganic compound, as needed other than a binder, for example.

  The first layer in the present invention is, for example, a thermoplastic resin (preferably latex, more preferably polyester urethane latex, acrylic silicone latex) as a binder in terms of suppressing penetration of the ink solvent and obtaining good surface properties. A layer in which kaolin is used as a white pigment and the mass ratio x / y of the mass (solid content) x of the thermoplastic resin to the mass y of the kaolin is 1 to 30, and further, an epoxy compound, an active methylene group A layer using a cross-linking agent selected from a compound having a cyanuric chloride, formaldehyde, and carbodiimide is preferable.

-Binder-
The first layer contains at least one binder. The binder is used for the purpose of improving not only the dispersion but also the coating film strength.
Examples of the binder include polyvinyl alcohol (including modified polyvinyl alcohols such as acetoacetyl modification, carboxy modification, itaconic acid modification, maleic acid modification, silica modification and amino group modification), methylcellulose, carboxymethylcellulose, starches (modified starch). ), Gelatin, arabic gum, casein, styrene-maleic anhydride copolymer hydrolyzate, polyacrylamide, saponified vinyl acetate-polyacrylic acid copolymer, and the like. Examples thereof also include latex binders of synthetic polymers such as styrene / butadiene copolymer, vinyl acetate copolymer, acrylonitrile / butadiene copolymer, methyl acrylate / butadiene copolymer, and polyvinylidene chloride.

  The polyvinyl alcohol includes polyvinyl alcohol obtained by saponifying a lower alcohol solution of polyvinyl acetate and derivatives thereof, and a saponified product of a copolymer of a monomer and vinyl acetate that can be copolymerized with vinyl acetate. It is. 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 ( Monoalkylmalates), olefinic sulfonic acid alkali salts such as sodium disulfonic acid alkylmalate, amide group-containing monomers such as N-methylolacrylamide, alkali acrylamide alkylsulfonic acid salts, and N-vinylpyrrolidone derivatives Can be mentioned.

  Of the polyvinyl alcohols, acetoacetyl-modified polyvinyl alcohol can be generally produced by adding and reacting a liquid or gaseous diketene to the solution, dispersion or powder of the polyvinyl alcohol resin. The acetylation degree of acetoacetyl-modified polyvinyl alcohol can be appropriately selected according to the intended quality, but is preferably 0.1 mol% to 20 mol%, more preferably 0.5 mol% to 10 mol%. It is.

  As the binder, polyolefins such as α-olefin homopolymers such as polyethylene, polypropylene and polyvinyl chloride or mixtures thereof; polyamides and polyimides; polyesters such as polyethylene terephthalate; and other general-purpose thermoplastic polymers , Α-methylene fats such as methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, dodecyl (meth) acrylate, octyl (meth) acrylate, phenyl (meth) acrylate, etc. Styrenes such as styrene, chlorostyrene and vinyl styrene; vinyl esters such as vinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate; vinyl methyl ether, vinyl ethyl ether, vinyl butyl ether, etc. Vinyl ether Homopolymers of vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone, vinyl isopropenyl ketone, etc., or arbitrary copolymers containing these structural units, and the like of known thermoplastic resins and their latexes. It can be suitably selected from the inside.

Among these, a thermoplastic resin is preferable and latex is more preferable in terms of water blocking properties. Latex includes acrylic latex, acrylic silicone latex, acrylic epoxy latex, acrylic styrene latex, acrylic urethane latex, styrene-butadiene latex, acrylonitrile-butadiene latex, polyester urethane latex, and vinyl acetate latex. And the like.
In particular, polyester-based urethane latex and acrylic silicone-based latex are preferable because they have high ink solvent permeability and cockling-suppressing effects and have both economic efficiency and production suitability.

  The molecular weight of the latex is preferably 3,000 to 1,000,000 in terms of number average molecular weight, and more preferably about 5,000 to 100,000. When the molecular weight is 3,000 or more, the mechanical strength of the first layer can be secured, and when it is 1,000,000 or less, it is advantageous in terms of production suitability such as dispersion stability and viscosity.

Specifically, 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 silicon 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 Aquabrid series UM7760, UM7611, UM4901, Aquabrid 903, Asi-86, ASi-89, Asi-91, ASi-753, 4635, 4901, MSi-04S, Chemical Industries, Ltd. AU-124, AU-131, AEA-61, AEC-69, AEC-162, etc.) can also be suitably used.
Examples of the polyester-based urethane latex include, as commercial products, HYDRAN AP series (for example, HYDRAN AP-20, AP-30, AP-30F, and AP-40 manufactured by Dainippon Ink & Chemicals, Inc.). (F), the same AP-50LM, the same APX-101H, the same APX-110, the same APX-501, etc.).
In addition, it is preferable to select and use at least one of the above thermoplastic resins from the above, and it may be used alone or in combination of two or more.

  The glass transition temperature (Tg) of the thermoplastic resin is preferably 5 to 70 ° C, and particularly preferably 15 to 50 ° C. When the Tg is particularly within the above range, problems such as burrs of the film forming liquid for forming the first layer (for example, coating liquid) are prevented, and handling in manufacturing is easy, and Tg is high. If the calendar temperature is not set too high, the desired gloss cannot be obtained, and adhesion to the metal roll surface is likely to occur. High planarity can be obtained.

  The minimum film-forming temperature of the thermoplastic resin (preferably latex resin fine particles) is preferably 20 to 60 ° C, and more preferably 25 to 50 ° C. When the minimum film forming temperature range where film formation is possible when trying to form a film is particularly within the above range, problems such as burrs of the film forming liquid for forming the first layer (for example, coating liquid) can be prevented. It is easy to handle in production, and the penetration when the second layer is formed is suppressed, the coated surface of the second layer to be formed is good, and the ink solvent can be quickly transmitted. A layer having sufficient microporosity can be formed. Although a layer only provided with a liquid (for example, a coating solution) does not necessarily have good glossiness, a high glossiness layer having microporosity can be obtained by performing a soft calender treatment later.

  As content in the 1st layer of a binder (preferably thermoplastic resin), 15-95 mass% is preferable with respect to the total solid of this 1st layer, and 30-90 mass% is more preferable. When the content is particularly within the above range, gloss and flatness are good when calendar treatment is performed, ink solvent permeability is obtained, and the occurrence of bleeding with time is more effectively prevented. Can do.

  Moreover, you may add the crosslinking agent of a suitable binder to a 1st layer according to the kind of these binder as needed.

-Cobb water absorption-
In the present invention, the Cobb water absorption at a contact time of 120 seconds measured by a water absorption test based on JIS P8140 on the surface of the first layer is 2.0 g / m ² or less.
When the Cobb water absorption is 2.0 g / m ² or less, the base paper provided with the first layer has a slow permeability and delays the absorption when a liquid such as ink is applied, thereby generating curls. Can be reduced.
Furthermore, the Cobb water absorption is more preferably 1.0 g / m ² or less. Further, the lower limit value of the Cobb water absorption is preferably 0.2 g / m ² .

  The Cobb water absorbency is measured by a water absorbency test in accordance with JIS P8140, and the first surface on the base paper provided with one side of the support, specifically, the first layer (binder-containing layer). This is a measure of the amount of water that is absorbed when water contacts the surface of the layer for a certain period of time. In the present invention, the contact time is 120 seconds.

<Example of First Layer Cobb Water Absorption Prediction Method for Second Layer Coated Product>
When the Cobb water absorption of the first layer is low, the second layer-forming coating solution at the time of coating the second layer (absorbing layer) is difficult to soak into the first layer. Therefore, the interface between the first layer and the second layer is relatively easy to understand.
The second layer is generally easily dyed by Magic Ink (registered trademark, sold by Teranishi Chemical Industry Co., Ltd.) and is easily dyed, but the first layer is made of, for example, styrene-butadiene or acrylic-urethane. When the latex is the main component or when the Cobb water absorption is 2 g / m ² or less, the magic ink (registered trademark) is difficult to permeate and is difficult to be dyed. Using such a phenomenon, after dyeing the second layer with magic ink (registered trademark, very thick), it is possible to scrape only the second layer with a razor blade or the like.
It is possible to predict the Cobb water absorption of the first layer after scraping the second layer by this method. However, because the sample cannot be cut uniformly due to the surface properties of the sample, the Cobb water absorption may increase due to the destruction of the first layer due to overcutting, or the Cobb water absorption measurement because the second layer remains. Since the value may be high, measurement is performed at least 5 times per sample, and the average value of 3 times excluding the maximum value and the minimum value is defined as the Cobb water absorption on the surface of the first layer.

The Cobb water absorption on the surface of the first layer after cutting the second layer is about 0.5 to 3 g / m ² from the Cobb water absorption on the surface of the first layer before providing the second layer. May be higher. Therefore, if the Cobb water absorption on the surface of the first layer after cutting the second layer is 5 g / m ² or less, the Cobb water absorption on the surface of the first layer before providing the second layer is ² g / m ^2. m ² or less.

Furthermore, from the dyeing behavior of the magic ink (registered trademark), if the water absorption on the surface of the first layer is 2 g / m ² or less, the magic ink (registered trademark) does not show off on the back surface. Or it becomes a grade where the spot which turns over in the shape of a spot is recognized. Therefore, if such behavior appears, it is estimated that the Cobb water absorption on the surface of the first layer is 2 g / m ² or less.

Subsequently, other components such as a white pigment, a hardener, and a layered inorganic compound will be described.
-White pigment-
Examples of white pigments 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 hydroxide. And magnesium.

  Further, kaolin other than calcined kaolin is particularly preferred from the viewpoint of water blocking. Such kaolins include Astra Plus, Contour 1500, Contour Extreme, Capim DG, Capim NP, Capim CC, Astra Scene, Astra Gross, Astra Coat, Beta Bright, Astra Glaze from Imeris Minerals Japan Co., Ltd. , Premier LX, Premier, Casey S, Astra Plate, XP03-8390, etc. Union clay RC-1, NN kaolin clay, SPMA clay, kaolin clay 5M, hard sill, ST kaolin clay, catalpo, No. 5 clay, etc. M.M. Huber's Huber35, Huber35B, Huber80, Huber80B, Huber90, Huber90B, HuberHG90, Huber TEK2001, Polygloss90, PolyplateP, Polyplate P01, Polythpe 94

  Further, when the first layer contains a white pigment, sticking to the calendar can be prevented when the calendar process is performed after the first layer is formed.

  The particle size of the white pigment is preferably 75% or more (volume basis) of particles having a size of 2.0 μm or less. When the particle size is within the above range, the whiteness and glossiness become good.

The specific surface area of the white pigment by the BET method is preferably less than 100 m ² / g. When a white pigment having a specific surface area in this range is included, the penetration of the coating liquid when the second layer is applied and formed can be suppressed, and the ink absorbability of the second layer can be increased.

  The BET method is one of powder surface area measurement methods by a gas phase adsorption method, and is a method for obtaining a total surface area, that is, a 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 Brunauer Emmett, Teller's formula (BET formula). Based on this formula, the amount of adsorption is obtained and the surface area is obtained by multiplying the area occupied by one adsorbed molecule on the surface. .

A white pigment can be used alone or in combination of two or more.
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., but is usually 5 to 200 mass with respect to the mass (solid content) of the binder. % Is desirable.

-Hardener-
The first layer of the present invention may contain a hardening agent for hardening the binder. As a hardener, an aldehyde compound, 2,3-dihydroxy-1,4-dioxane and its derivatives, and a vinyl group adjacent to a substituent whose Hammett's substituent constant σ _p is positive are contained in a single molecule. It can be selected from compounds having two or more.
By containing a hardener in the first layer, the water resistance of the recording medium can be improved without increasing the viscosity of the film-forming liquid for forming the first layer. As a result, the coating stability of the film-forming liquid for forming the first layer is improved, and the water resistance of the produced recording medium is also improved.

The substituents having a positive Hammett's substituent constant σ _p include CF ₃ group (σ _p value: 0.54), CN group (σ _p value: 0.66), COCH ₃ group (σ _p value: 0). .50), COOH group (σ _p value: 0.45), COOR (R represents an alkyl group) group (σ _p value: 0.45), NO ₂
Group (σ _p value: 0.78), OCOCH ₃ group (σ _p value: 0.31), SH group (σ _p value: 0.
15), SOCH ₃ group (σ _p value: 0.49), SO ₂ CH ₃ group (σ _p value: 0.72), SO ₂ NH ₂ group (σ _p value: 0.57), SCOCH ₃ group ( σ _p value: 0.44), F group (σ _p value: 0.06), Cl group (σ _p value: 0.23), Br group (σ _p value: 0.23), I group (σ _p Value: 0.18), IO ₂ group (σ _p value: 0.76), N ⁺ (CH ₃ ) ₂ group (σ _p value: 0.82), S ⁺ (CH ₃ ) ₂ group (σ _p value) : 0.90) and the like.

The compound having two or more vinyl groups adjacent to a substituent having a positive Hammett's substituent constant σ _p 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 hardener in the first layer is preferably 0.1% by mass to 30% by mass, and more preferably 0.5% by mass to 10% by mass with respect to the solid content of the binder. When the content of the hardener is within the above range, the film-forming liquid for forming the first layer does not thicken, and the water resistance of the recording material can be improved.

-Layered inorganic compound-
The first layer may further contain a layered inorganic compound. As the layered inorganic compound, a swellable inorganic layered compound is preferable, for example, swelling viscosity minerals such as bentonite, hectorite, saponite, beiderite, nontronite, stevensite, beidellite, montmorite, swellable synthetic mica, swellable synthesis Examples include smectite. The swellable inorganic layered compound has a laminated structure consisting of unit crystal lattice layers with a thickness of 1 to 1.5 nm, and the lattice layer is insufficiently positively charged because the substitution of metal atoms in the lattice is significantly larger than other clay minerals. In order to compensate for this, cations such as Na ⁺ , Ca ²⁺ and Mg ²⁺ are adsorbed between the layers. 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 bonds between the layered crystal lattices are weak, and the layers swell greatly with water. If shear is applied in this state, it will easily cleave and form a stable sol in water. Bentonite and swellable synthetic mica are preferred in that this tendency is strong. 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 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. Therefore, the aspect ratio is preferably 100 or more, more preferably 200 or more, and particularly preferably 500 or more.

When the water-swellable synthetic mica is used, the mass ratio x / y between the mass (solid content) x of the binder in the first layer and the mass y of the water-swellable synthetic mica is preferably in the range of 1 to 30. The range of 5 or more and 15 or less is more preferable. When the mass ratio is within the above range, the effect is great in suppressing oxygen permeation and blistering.
In addition, well-known additives, such as antioxidant, can also be added to a 1st layer.

  The thickness of the first layer is preferably in the range of 1 to 30 μm, and more preferably in the range of 5 to 20 μm. When the thickness of the first layer is within the above range, the glossiness of the surface when calendering is performed later is improved, whiteness can be obtained with a small amount of white pigment, and handleability such as bendability. Can be equivalent to coated paper or art paper.

(Second layer)
The recording medium of the present invention further has a second layer on the first layer on the base paper.
The second layer includes at least kaolin, polyvinyl alcohol having a polymerization degree of 1500 or more and 8000 or less, and polyvinyl alcohol having a polymerization degree of 100 or more and less than 1500, and the absorption capacity of diethylene glycol on the surface of the second layer is 2 mL / m ² or more and 8 mL. / M ² or less.
If it is this range, there will be no restriction | limiting in particular, As a 2nd layer, it can select suitably from well-known things according to the objective.
In addition, the second layer can be constituted by using other components such as a thermoplastic resin as necessary.

  The second layer in the present invention includes, for example, a layer further containing a thermoplastic resin, a layer further containing a thermoplastic resin having a solid mass of 10 to 60 parts per 100 parts of the solid mass of kaolin, and a pH of the layer surface of 4 or less. It is preferable that the layer is.

-Kaolin-
The second layer contains at least one kaolin. By containing kaolin, the ink (particularly the pigment in the ink) can be retained in the second layer, and the background whiteness is also increased.

  As kaolin contained in the second layer, in terms of image bleeding, color mixing prevention, and film strength, Astra Plus, Contour 1500, Contour Extreme, Capim DG, Capim NP of Imerizu Minerals Japan Co., Ltd. , Capim CC, Astra Scene, Astra Gross, Astra Coat, Beta Bright, Astra Glaze, Premier LX, Premier, Casey S, Astra Plate, XP03-8390, etc. Khao White S, Khao White, Khao White C, Khao Fine, Kao Gloss, Kaoblite, etc. catarrh , No. 5 clay, etc., J. M.M. Huber's Huber35, Huber35B, Huber80, Huber80B, Huber90, Huber90B, HuberHG90, Huber TEK2001, Polygloss90, PolyplateP, Polyplate P01, Polythpe 94

The kaolin preferably has a whiteness of more than 87, more preferably 90 or more. If the whiteness of the kaolin exceeds 87, it is possible to effectively prevent the image receiving paper from being colored and maintain the high-quality feeling of the paper for a long time.
The particle size of kaolin contained in the second layer is preferably a composition ratio (volume ratio) of kaolin having a particle size of 2 μm or less, preferably 75% or more, more preferably 80% or more. If the proportion of kaolin having a particle size of 2 μm or less is 75% or more, the gloss is high and a high-quality paper can be produced.

  As content in a 2nd layer of a kaolin, 75-99 mass% is preferable with respect to the total solid of a 2nd layer, and 80-96 mass% is more preferable.

-Baking kaolin-
The second layer preferably further contains calcined kaolin.
The calcined kaolin is anhydrous aluminum silicate which is made amorphous by heating natural kaolin at a high temperature in a calcining furnace to remove crystal water. Examples of the calcined kaolin include Alphatex and Opatitex manufactured by Imeris Minerals Japan, Kaocal manufactured by Shiraishi Calcium Co., Ltd., Ancilex 93 manufactured by Engelhard, and the like.

In the second layer, the content of the calcined kaolin is preferably 10% by mass or more based on the total amount of the pigment in the second layer. When the content in the second layer is less than 10% by mass, the recorded ink image is easily peeled off due to insufficient fixability of the ink, and sticks to the fixing roll when coming into contact with the fixing roll. The image may be damaged.
As the content of the calcined kaolin, the ink absorption is imparted to the total amount of the pigment in the second layer, the ink (particularly the pigment in the ink) is kept in the second layer, and the background whiteness is further increased. From the viewpoint of imparting the fixability (hardness of peeling) of the recorded ink image while increasing, the range of 10 to 70% by mass is preferable, and the range of 20 to 50% by mass is more preferable.

Further, in the second layer, white pigments other than kaolin and calcined kaolin, such as titanium oxide, barium sulfate, barium carbonate, calcium carbonate, lithopone, alumina white, zinc oxide, silica, so as not to impair the effects of the present invention Antimony trioxide, titanium phosphate, aluminum hydroxide, clay, talc, magnesium oxide, magnesium hydroxide, and the like can also be included.
When an image is formed by applying the recording medium of the present invention to the first or second ink jet recording method of the present invention described later, that is, the pH of the surface of the second layer is set to the acidic side (preferably 4 or less). ) Or when performing ink drawing using a treatment liquid containing an acidic substance, which will be described later, from the viewpoint of avoiding bleeding and color mixing of the image when the ink is drawn, the content of calcium carbonate is The amount is preferably 1% by mass or less based on the total pigment in the layer, and more preferably contains no calcium carbonate.

-Polyvinyl alcohol-
The second layer contains polyvinyl alcohol having a polymerization degree of 1500 or more and 8000 or less and at least one polyvinyl alcohol having a polymerization degree of 100 or more and less than 1500.
The two types of polyvinyl alcohol will be described below, but the common part will be described simply as polyvinyl alcohol.
The polyvinyl alcohol contained in the second layer is not particularly limited, and a polyvinyl alcohol obtained by saponifying a lower alcohol solution of polyvinyl acetate and a derivative thereof can be further copolymerized with vinyl acetate and a monomer. A saponified product of the above can be used. 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 ( Monoalkylmalates), olefinic sulfonic acid alkali salts such as sodium disulfonic acid alkylmalate, amide group-containing monomers such as N-methylolacrylamide, alkali acrylamide alkylsulfonic acid salts, and N-vinylpyrrolidone derivatives Can be mentioned.

For example, modified polyvinyl alcohols such as acetyl modification, carboxy modification, itaconic acid modification, maleic acid modification, silica modification, and amino group modification can also be used.
For example, acetoacetyl-modified polyvinyl alcohol 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 second layer freely expands and contracts even in a process that requires heating, does not generate cracks, and does not easily generate blisters.
The modification rate of the 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, and 0.05 to 15 mol. % Is more preferable.

The degree of polymerization of polyvinyl alcohol having a polymerization degree of 1500 or more and 8000 or less contained in the second layer is preferably 3000 or more and 8000 or less.
The PVA contained in the second layer tends to agglomerate when a pigment is added if only a polymer having a high degree of polymerization is used, and if only a polymer having a low degree of polymerization is used, the strength of the coating film and the coating film during printing are weakened. As a printed matter, the coating film becomes weak. For these reasons, it is necessary to use PVA with a high degree of polymerization and PVA with a low degree of polymerization.

  Moreover, the saponification degree of polyvinyl alcohol is not particularly limited, but is preferably 85% or more, and more preferably 87 to 99%. When the saponification degree of polyvinyl alcohol is 85% or more, the water resistance effect can be remarkably enhanced.

  The polymerization degree (high polymerization degree) of polyvinyl alcohol having a polymerization degree of 1500 to 8000 contained in the second layer is 3000 to 8000, and the polymerization degree of polyvinyl alcohol having a polymerization degree of 100 to less than 1500 (low polymerization degree). Is preferable from the viewpoint of coating strength.

  The mass ratio b / a between the mass a of polyvinyl alcohol (solid content) and the mass b of kaolin contained in the second layer is preferably 2: 1 to 30: 1, more preferably 3: 1 to 25: 1. 5: 1 to 20: 1 are particularly preferred. When the mass ratio b / a between polyvinyl alcohol and kaolin is 2: 1 to 30: 1, oxygen permeation and blistering are suppressed, and good surface properties are obtained, and ink peeling is effectively suppressed. can do.

-SBR-
In addition to the above components, the second layer preferably further contains SBR (styrene-butadiene copolymer rubber) from the viewpoints of ink permeability and film strength.

  Specifically, examples of the SBR latex include SN307 (manufactured by Nippon A & L Co., Ltd.).

As content in the 2nd layer of SBR, 1-20 mass% is preferable with respect to the total solid of this 2nd layer, and 3-10 mass% is more preferable.
When the content is particularly within the above range, the ink permeability and the film strength tend to be good.

-Thermoplastic resin-
The second layer may contain other components such as a thermoplastic resin other than the above components.
There is no restriction | limiting in particular as a thermoplastic resin, For example, the thermoplastic resin similar to what was mentioned by the above-mentioned 1st layer can be used.

~ Measurement of absorption capacity of diethylene glycol (DEG) ~
In the present invention, the absorption capacity of diethylene glycol (DEG) on the surface of the second layer is 2 mL / m ² or more and 8 mL / m ² or less under the measurement conditions.
When the absorption capacity is ² to 8 mL / m ² , the second layer is slowly permeable, delays liquid absorption on the application surface when liquid such as ink is applied, and suppresses the degree of curling. In addition, image bleeding and color mixing between colors can be prevented. To prevent image bleeding and color mixing between colors, the pH of the surface of the second layer is adjusted to acidic (particularly pH 4 or lower), or a treatment liquid containing an acidic substance described later is used together with ink as described later. Is particularly effective.
Absorption capacity of the diethylene glycol (DEG), the curl prevention, in view of image bleeding and color mixing prevention 3 mL / ^{m 2} or more ~ 5 mL / ^{m 2} or less is more preferable.

The method for measuring the absorption capacity of diethylene glycol (DEG) employs the following method.
That is, 1 mL of diethylene glycol was dropped on the ink receiving layer of a test piece obtained by cutting the recording medium so as to be 10 cm square, and after 30 seconds, the excess was wiped off, and the diethylene glycol absorption capacity (mL / M ² ).

~ PH ~
The second layer is preferably adjusted to have a pH of 4 or less on the surface of the layer, thereby aggregating the applied ink and improving the fixing of the ink. That is, for example, in the case of an ink containing a pigment as a coloring component, the pigment aggregates due to a change in pH when it drops on the second layer, and it is possible to prevent ink bleeding with time and color mixing between colors.

As a compound for acidifying the surface of the second layer, a compound having a phosphoric acid group, a phosphonic group, a phosphine group, a sulfuric acid group, a sulfonic acid group, a sulfinic acid group, a carboxylic acid group or a salt-derived group is used. It is preferable to use a compound having a phosphoric acid group or a carboxylic acid group.
For example, the compound having a phosphate group includes phosphoric acid, polyphosphoric acid, derivatives of these compounds, or salts thereof, and the compound having a carboxylic acid group includes furan, pyrrole, pyrroline, pyrrolidone, pyrone, A compound having a pyrrole, thiophene, indole, pyridine, quinoline structure and further having 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, There are thiophenecarboxylic acid, nicotinic acid, derivatives of these compounds, or salts thereof.
By adding these compounds to the film forming solution for forming the second layer, the pH can be adjusted to 4 or less. What is necessary is just to select the addition amount suitably so that pH may become 4 or less.

  The pH can be measured by the A method (coating method) of the measurement of the film surface PH determined by the Japan Paper Pulp Technology Association (J.TAPPI paper). For example, Kyoritsu Co., Ltd., which corresponds to the A method, This can be done using a PH measurement set for paper “Type MPC” manufactured by RIKEN. In the type MPC, the test liquid is spread on the paper surface and the color is measured by comparing with the standard color.

  As thickness of a 2nd layer, the range of 3-50 micrometers is preferable, and the range of 4-40 micrometers is more preferable. When the thickness of the second layer is within the above range, it is preferable in terms of preventing image bleeding and color mixing between colors.

(Other layers)
In the recording medium of the present invention, other layers other than the first and second layers may be provided as other layers. Other layers can be appropriately selected depending on the purpose.

<Method for manufacturing recording medium>
In the recording medium manufacturing method for manufacturing the recording medium of the present invention described above (the recording medium manufacturing method of the present invention), a first layer is formed by applying a film-forming solution containing a binder on a base paper. And forming a second layer on the first layer by applying a film-forming solution containing kaolin, polyvinyl alcohol having a polymerization degree of 1500 to 8000 and polyvinyl alcohol having a polymerization degree of 100 to less than 1500. 2 and the second layer is formed by adding a pigment dispersion containing kaolin to polyvinyl alcohol having a polymerization degree of 100 or more and less than 1500, and then having a polymerization degree of 1500 or more and 8000 or less. It is obtained by adding polyvinyl alcohol.
The recording medium manufacturing method of the present invention may further include other processes appropriately selected as necessary.

The coating amount (solid content) of the film-forming solution for forming the first layer and the film-forming solution for forming the second layer in the present invention can be appropriately selected according to the purpose.
In the present invention, the solid content coating amount of the first layer coating solution is not particularly limited, but is preferably ² to ²⁰ g / m ² from the viewpoint of Cobb water absorption and coating surface shape, and 4 to 15 g / m ^2. Is more preferable.
In the present invention, is not particularly limited in the solid coating amount of the second layer coating liquid, from the viewpoint of DEG absorption capacity and coating surface, preferably ^{4~30g / m 2, 6~20g / m} 2 Is more preferable.
Furthermore, in the present invention, the coating amount of the first coating liquid is ² to 20 g / m ² (preferably 4 to 15 g / m ² ), and the solid content coating amount of the second layer coating liquid is 4 to 4 g. 30 g / ^{m 2} (preferably 6~20g / ^{m 2)} is more preferable.

-First forming step-
In the first forming step, a first layer is formed by applying a film-forming solution containing a binder (a first layer-forming film-forming solution) on the base paper. Preferably, the heat treatment is performed in a temperature range equal to or higher than the minimum film forming temperature of the binder. In the heat treatment, pressure may be applied.

The details of the base paper are as described in the first layer described above, and the preferred embodiments are also the same.
The binder (and its particles) is preferably a thermoplastic resin, more preferably a latex thereof, and the same binders that can be used in the first layer described above can be exemplified, and there is no particular limitation. . A binder may be used individually by 1 type and may use 2 or more types together.

  The binder preferably has an average particle size of 10 to 200 nm. Here, the average particle diameter of the binder is a value measured by a dynamic light scattering method (device name: ELS-800, manufactured by Otsuka Electronics Co., Ltd.).

The thermoplastic resin constituting the binder preferably has a minimum film forming temperature (MFT) of 5 ° C to 60 ° C.
The coating amount of the binder is preferably ¹ to 30 g / m2.

  As the thermoplastic resin particles, those containing water-dispersible latex-dispersed particles are preferable from the viewpoints of suppression of cockling, improvement of bleeding over time, production suitability, and the like. The water-dispersible latex is obtained by dispersing a hydrophobic polymer insoluble or hardly soluble in water as fine particles in a water-phase dispersion medium. This dispersion state may be a polymer that is emulsified in a dispersion medium, an emulsion polymerized, a micelle-dispersed, or a polymer molecule that has a partially hydrophilic structure and the molecular chain itself is molecular. Any of those dispersed may be used. For such water-dispersible 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 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 polyester urethane latex, acrylic latex, acrylic silicone latex, acrylic epoxy latex, acrylic styrene latex, acrylic urethane latex, styrene-butadiene latex, and acrylonitrile. Preferable examples include at least one selected from butadiene latex and vinyl acetate latex.

The molecular weight of the water-dispersible latex is preferably 3,000 to 1,000,000 in terms of number average molecular weight, and more preferably about 5,000 to 100,000. When the molecular weight is 3,000 or more, the mechanical strength of the first layer can be secured, and when it is 1,000,000 or less, it is advantageous in terms of production suitability such as dispersion stability and viscosity.
Among the water-dispersible latexes, the first layer is selected from polyester-based urethane latex and acrylic silicone-based latex from the viewpoint that the ink solvent permeability and the effect of suppressing cockling are high and the economy and manufacturing suitability can be combined. 1 type or 2 types or more are most preferable.

The application of the first layer-forming film-forming liquid is not particularly limited as long as it is a film-forming method, and can be performed by any known method such as a coating method, an ink-jet method, or an immersion method. In view of the smoothness of the film surface, it is preferable to use a coating method using the first layer-forming film forming solution as a coating solution.
As the coating method, a known coating method can be applied. Examples of the known coating method include a blade coating method, a slide bead method, a curtain method, an extrusion method, an air knife method, a roll coating method, and a Ked bar coating method. Is mentioned.

  After coating, the coating film formed by coating is subjected to heat treatment in a temperature range equal to or higher than the minimum film forming temperature of the binder. The heat treatment may be performed in combination with the drying treatment after coating, or may be performed separately. The heat treatment can be performed, for example, by a method such as placing in an oven having a temperature equal to or higher than the minimum film-forming temperature or applying a drying air having a temperature equal to or higher than the minimum film-forming temperature.

-Second forming step-
In the second forming step, on the first layer formed in the first forming step, kaolin that forms the second layer, polyvinyl alcohol having a polymerization degree of 1500 to 8000, and a polymerization degree of 100 to less than 1500 A film forming liquid containing polyvinyl alcohol (second film forming liquid for forming a layer) is applied to form a second layer. In this case, the second layer-forming film-forming solution is obtained by adding the pigment dispersion containing the kaolin to the polyvinyl alcohol having the polymerization degree of 100 or more and less than 1500, and then adding the polyvinyl alcohol having the polymerization degree of 1500 or more and 8000 or less. It is characterized by being obtained.
The coating properties are improved by preparing the second layer-forming film forming solution by the operation method as described above.
Specifically, the second layer-forming film forming solution can be prepared as follows.
First, water and a white pigment (kaolin, calcined kaolin, etc.) are mixed and dispersed in water to prepare a pigment dispersion. Under the present circumstances, the additive (polyacrylic acid Na etc.) which can be contained in the said 2nd layer as needed can be added in the range which does not impair the effect of this invention.
Next, this pigment dispersion is added to an aqueous solution of PVA having a low polymerization degree (polyvinyl alcohol having a polymerization degree of 100 to less than 1500), and further added to this liquid to a high polymerization degree PVA (polyvinyl alcohol having a polymerization degree of 1500 to 8000). It can adjust by adding the aqueous solution.
If necessary, an additive (SBR) and other additives (surfactant, etc.) that can be contained in the second layer are added to the aqueous solution of the high polymerization degree PVA as long as the effects of the present invention are not impaired. can do. In addition, the film-forming solution may be prepared by adding other steps such as filter filtration as necessary.
There is no restriction | limiting in particular except these, According to the objective, it can select suitably.

The application of the second layer forming film forming liquid is not particularly limited as long as it is a film forming method, and can be performed by any known method such as a coating method, an ink jet method, or an immersion method. It is preferable to use a coating method using the second layer-forming film forming solution as a coating solution in that the film surface is smooth and high gloss is obtained.
As a coating method, a known coating method can be applied. Examples of the known coating method include a blade coating method (vent method, bevel method), a slide bead method, a curtain method, an extrusion method, an air knife method, and roll coating. Examples thereof include a method and a Ked bar coating method. Among the coating methods described above, the curtain method is a preferable mode because high-speed coating is possible and the range corresponding to the coating thickness is wide. Also, a blade coating method is a preferred embodiment in that high-speed coating is possible, and when a flat pigment such as a layered inorganic compound is used, for example, gloss can be obtained by promoting its orientation. In addition, the blade coating method generates a relatively large shear stress at the moment of scraping, so that a large amount of water can easily move into the paper support due to the pressurization and penetration due to the instantaneous nip pressure, but the solvent penetration is blocked. The recording medium of the present invention having the first layer is particularly effective.

  In addition to the above steps, other steps may be provided without particular limitation. Other steps can be appropriately selected according to the purpose.

<Inkjet recording method>
The ink jet recording method of the present invention includes an ink drawing process in which ink is applied to the recording medium of the present invention described above and ink is drawn according to predetermined image data, and an ink solvent in the ink drawn ink is dried. It is possible to provide a dry removal step for removal.
Among the ink jet recording methods described above, among the recording media of the present invention described above, the second layer (coating layer on the first layer) is preliminarily incorporated with an aggregating agent (treatment liquid) to lower the pH of the layer surface. It is preferable that the ink jet recording method (see FIG. 2; hereinafter referred to as “the ink jet recording method according to the first aspect”) in which ink is drawn on the recording medium.
In addition, an ink jet recording method for drawing ink after supplying a treatment liquid containing an acidic substance (pre-coating) to the recording medium of the present invention described above (see FIG. 3; hereinafter, “ink jet according to second embodiment” The recording method is preferred.).

In the ink jet recording method according to the first aspect of the present invention, ink is applied to the recording medium of the present invention in which the surface of the second layer is adjusted to pH 4 or less, and ink drawing is performed according to predetermined image data. An ink drawing process and a dry removal process for drying and removing the ink solvent in the ink-drawn recording medium are provided.
In addition, the ink jet recording method according to the second aspect of the present invention includes a processing liquid supply step of supplying a processing liquid containing an acidic substance to the recording medium of the present invention described above, and the recording medium supplied with the processing liquid. And an ink drawing process for drawing ink according to predetermined image data, and a drying removal process for drying and removing the ink solvent in the ink-drawn recording medium.
Any of the inkjet recording methods according to the first and second aspects described above may further include other steps selected as appropriate.

-Ink drawing process-
The ink drawing process of the first aspect uses the recording medium of the present invention in which the layer surface of the second layer is adjusted to pH 4 or less, among the recording media of the present invention described above. By applying ink to the layer, ink is drawn according to predetermined image data. When ink (for example, pigment ink) is applied to the second layer, the ink (for example, pigment in the ink) aggregates due to pH change at the time of landing, thereby preventing ink bleeding and color mixing between colors. The

  In the ink drawing step of the second aspect, the processing liquid is supplied in the following processing liquid supply step without adjusting or adjusting the layer surface pH of the second layer to 4 or less as in the first aspect. By applying ink to the recording medium, ink drawing is performed according to predetermined image data. In the second aspect, at least a part of the second layer is in an acidic state (preferably pH 4 or less) by the treatment liquid supplied to the second layer before applying the ink or simultaneously with applying the ink. The ink (for example, pigment ink) applied here undergoes a pH change at the time of landing, and the ink (for example, pigment in the ink) aggregates, thereby preventing ink bleeding and color mixing between colors.

The ink drawing process is not particularly limited except that ink is drawn according to predetermined image data, and can be appropriately selected according to the purpose. For example, ink can be drawn by ejecting ink by an inkjet method. There are no particular restrictions on the ink jet recording system, for example, a charge control system that ejects ink using electrostatic attraction, a drop-on-demand system (pressure pulse system) that uses the vibration pressure of a piezo element, and an electrical signal. Either an acoustic ink jet method that irradiates ink using an acoustic beam instead of an acoustic beam and ejects ink using radiation pressure, or a thermal ink jet method that uses ink to form bubbles by heating ink and generate pressure. May be. The inkjet recording method includes a method of ejecting a large number of low-density inks called photo inks in a small volume, a method of improving image quality using a plurality of inks having substantially the same hue and different concentrations, and colorless and transparent. A method using ink.
Among these, the drop-on-demand method (pressure pulse method) using a piezoelectric element is suitable.

-Processing liquid supply process-
In the ink jet recording method according to the second aspect, the treatment liquid supply step is provided before the ink drawing step or as a step simultaneously with the ink drawing, and the treatment liquid containing an acidic substance in the second layer of the recording medium in advance. Supply. The treatment liquid supply step is not particularly limited except that a treatment liquid containing the following acidic substance is supplied, and can be appropriately selected according to the purpose. Further, this treatment liquid supply step may be provided in the ink jet recording method according to the first aspect, if necessary.

(Processing liquid)
The treatment liquid containing an acidic substance may be any liquid that contains an acidic substance and is adjusted so as to have acidity, and is preferably an aqueous treatment liquid in which an acidic substance is mixed with an aqueous medium. The pH of the treatment liquid in the present invention is preferably 4 or less from the viewpoint of preventing ink bleeding and color mixing between colors.

As the acidic substance for constituting the treatment liquid acidic, a divalent or higher acid is preferable. For example, a compound having a phosphate group, a phosphonic acid group, a phosphinic acid group, a sulfuric acid group, a sulfonic acid group, a sulfinic acid group, a carboxylic acid group or a group derived from a salt thereof can be used. A compound having an acid group is more preferred, and a compound having a carboxylic acid group is still more preferred.
For example, the compound having a phosphate group includes phosphoric acid, polyphosphoric acid, derivatives of these compounds, or salts thereof, and the compound having a carboxylic acid group includes furan, pyrrole, pyrroline, pyrrolidone, pyrone, A compound having a pyrrole, thiophene, indole, pyridine, quinoline structure and further having 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, Thiophenecarboxylic 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, an acidic substance may be used by 1 type and may be used together 2 or more types.

The treatment liquid may contain other additives as long as the effects of the present invention are not impaired.
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.

  The treatment liquid may be supplied to the entire recording surface of the recording medium, or may be supplied according to at least a part of the recording surface, for example, predetermined image data. Moreover, there is no restriction | limiting in particular in the supply method of a process liquid, A coating method, an inkjet method, a dipping method etc. are mentioned, For example, you may discharge and supply a process liquid by the inkjet method.

  In the ink jet recording method according to the second aspect, drawing may be performed using an aqueous two-liquid aggregation ink described later.

-Dry removal process-
In the drying and removing step, the ink solvent in the recording medium on which ink has been drawn is removed by drying. There is no particular limitation other than drying and removing the ink solvent of the ink applied to the recording medium, and it can be appropriately selected according to the purpose.
In the recording medium of the present invention, the drying removal step is performed in a state where the ink solvent (particularly water) is present near the surface of the recording medium because the coat layer as the second layer is slowly permeable. The drying and removal can be performed by, for example, a method of applying a drying air at a predetermined temperature, a method of passing a heated and / or pressurized roll pair, or the like.

-Other processes-
The inkjet recording method of the present invention may be provided with other steps in addition to the above steps. There is no restriction | limiting in particular as another process, According to the objective, it can select suitably. For example, a heat fixing step may be mentioned.

  The ink jet recording method of the present invention may be provided with a heat fixing step of melting and fixing latex particles contained in, for example, ink used in the ink jet recording method after the drying and removing step. By this heat fixing step, the fixing property of the ink to the recording medium can be improved. The heat fixing step is not particularly limited except for the above-described melt fixing, and can be appropriately selected according to the purpose.

-Aspect example of first ink jet recording method-
In the first ink jet recording method, for example, ink drawing, drying (water drying, blow drying), and heat fixing can be performed under the following conditions.
<Ink drawing>
Head: 1,200 dpi / 20 inch width full line head Discharge droplet volume: 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)
<Heat fixing>
Silicone rubber roller (hardness 50 °, nip width 5mm)
Roller temperature: 70-90 ° C
Pressure: 0.5-2.0 MPa

-Aspect example of second ink jet recording method-
In the second ink jet recording method, for example, pre-coating, ink drawing, drying (water drying, blow drying), and heat fixing can be performed under the following conditions.
<Head for treatment liquid for precoat module>
Head: 600 dpi / 20ichi width 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 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 (air blowing drying)>
Wind speed: 8-15m / s
Temperature: 40-80 ° C
Air blowing area: 450 mm (drying time 0.7 seconds)
<Ink drawing>
Head: 1200 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)
<Heat fixing>
Silicone rubber roller (hardness 50 °, nip width 5mm)
Roller temperature: 70-90 ° C
Pressure: 0.5-2.0 MPa

-Aqueous two-liquid aggregation ink-
In the ink jet recording method according to the second aspect, an aqueous two-liquid aggregation ink comprising a treatment liquid and an ink that reacts and aggregates with the treatment liquid may be used.
As the treatment liquid for the aqueous two-liquid aggregation ink, the same treatment liquid as described above can be used. Details of the treatment liquid are as described above.

-Ink-
The ink constituting the aqueous two-liquid aggregation 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 particles such as a polymer of a compound composed of a nonionic monomer, an anionic monomer, and a cationic monomer dispersed in an aqueous medium.

  The said nonionic monomer means the monomer compound which does not have a dissociative functional group. In the broad sense, the monomer compound means a compound that is polymerized alone or with another compound. The monomer compound is preferably a monomer compound having an unsaturated double bond.

  The anionic monomer means a monomer compound containing an anionic group that can have a negative charge. 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 monomer means a monomer containing a cationic group that can have a positive charge. 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, it is more preferably a pyridinium cation or an ammonium cation.

<Organic pigment>
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 U.S. 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.

  Further, the average particle diameter of the organic pigment is preferably as small as possible from the viewpoint of transparency and color reproducibility, but is preferably large from the viewpoint of light resistance. As an average particle diameter which balances these, 10-200 nm is preferable, 10-150 nm is more preferable, 10-100 nm is further 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, further preferably 5 to 20% by mass, and particularly 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 that combines these.
The anionic group may be any as long as it has a negative charge, and 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, A phosphoric acid group and a carboxylic acid group are more preferable, and a carboxylic acid group is further preferable.
The cationic group may be any as long as it has a positive charge, and is preferably an organic cationic substituent, more preferably a nitrogen or phosphorus cationic group. Further, it is more preferably a pyridinium cation or an ammonium cation.
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 determined experimentally from a titration curve by titrating a solution obtained by dissolving 1 mmol / L of the low molecular dispersant in a tetrahydrofuran-water (3: 2 = V / V) solution with an acid or alkaline aqueous solution. It is the value. 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 agglutination 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, fluorocarbon-based, or silicone-based structure, 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 further preferably a hydrocarbon group having 6 to 20 carbon atoms.

  Of the polymer dispersants, hydrophilic polymer compounds can be used as the water-soluble dispersant. For example, natural hydrophilic polymer compounds include plant polymers such as gum arabic, tragan gum, guar gum, karaya gum, locust bean gum, arabinogalactone, pectin, quince seed starch, seaweeds such as alginic acid, carrageenan and agar. Examples include molecules, animal polymers such as gelatin, casein, albumin and collagen, and microorganism polymers such as xanthene gum and dextran.

  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. It is.

  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 in the range of 1: 0.125 to 1: 2, and still more preferably 1: 0.125. ~ 1: 1.5.

<Water-soluble organic solvent>
The water-soluble organic solvent is used for the purpose of preventing drying and promoting wetting.
A water-soluble organic solvent as a drying inhibitor is suitably used at an ink jet port of a nozzle in an ink jet recording system, and prevents clogging due to drying of the ink for ink jet.

  As the drying inhibitor, a water-soluble organic solvent having a vapor pressure lower than that of water is preferable. Specific examples of such an anti-drying agent include ethylene glycol, propylene glycol, diethylene glycol, polyethylene glycol, thiodiglycol, dithiodiglycol, 2-methyl-1,3-propanediol, 1,2,6- Hexanetriol, acetylene glycol derivatives, polyhydric alcohols such as glycerin and trimethylolpropane, ethylene glycol monomethyl (or ethyl) ether, diethylene glycol monomethyl (or ethyl) ether, triethylene glycol monoethyl (or butyl) ether, etc. Lower alkyl ethers of polyhydric alcohols, 2-pyrrolidone, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, heterocyclic rings such as N-ethylmorpholine, sulfolane, Methyl 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 drying inhibitor 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.

  In addition, a water-soluble organic solvent as a penetration accelerator is preferably used for the purpose of allowing the ink to penetrate better into the recording medium (printing paper). Specific examples of such 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 properties. A surfactant or the like can be suitably used. 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. The compounds described in No. 24239, compounds that emit fluorescence by absorbing ultraviolet rays typified by stilbene-based compounds 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 an amount of 0.02 to 1.00% by weight in the ink.

  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.

  Also, fluorine (fluorinated alkyl) surfactants, silicone surfactants, and the like described in JP-A Nos. 2003-322926, 2004-325707, and 2004-309806 are disclosed. By using, the abrasion resistance can be improved.

  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 Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to the following examples unless it exceeds the gist thereof. Unless otherwise specified, “part” and “%” are based on mass, and “polymerization degree” represents “average polymerization degree”.

Example 1
<Preparation of inkjet recording medium>
(Preparation of first layer-forming coating solution)
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.). To obtain a 65% kaolin dispersion. Subsequently, 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 5 parts, 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. The temperature was maintained at 15 to 25 ° C. to obtain a first layer coating solution having a solid content concentration of 24.0%.

(Preparation of second layer forming coating solution)
2000 parts of water, kaolin (trade name: Kaoblite 90, manufactured by Shiraishi Calcium Co., Ltd.) 1500 parts, calcined kaolin (trade name: Kao Cal, manufactured by Shiraishi Calcium Co., Ltd.), and 40% sodium polyacrylate (product) Name: Aron T-50, 50 parts by Toagosei Co., Ltd.) was mixed and dispersed in water.
This pigment dispersion was added to 800 parts of a 7.5% PVA105 (average polymerization degree 500, manufactured by Kuraray Co., Ltd.) aqueous solution. Furthermore, 2000 parts of an aqueous solution of 5% PVA145 (average polymerization degree 4,500, manufactured by Kuraray Co., Ltd.) and 300 parts of 48% SBR (trade name: SN307, Nippon A & L Co., Ltd.), 10% Aerosol MA80 (American Cyanamid Co., Ltd.) )) 200 parts of aqueous solution and 200 parts of 2% Lapisol A-90 (manufactured by NOF Corporation) are added to form a second layer-forming coating solution a having a final solid content concentration of 31%. Prepared.

(First layer formation)
The first layer coating liquid obtained was passed through a 150 mesh pole filter on both sides of high-quality paper with a basis weight of 81.4 g / m ² (trade name: Shiraoi, manufactured by Nippon Paper Industries Co., Ltd.). , And apply one side at a time while adjusting the coating amount per side to 8.0 g / m ^2, and dry for 1 minute at a temperature of 85 ° C. and a wind speed of 15 m / sec to form the first layer. did. Furthermore, the soft calendar process shown below was performed with respect to the formed 1st layer. The thickness of the formed first layer was 8.1 μm.

~ 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 fine paper having the first layer formed on the surface, the surface temperature of the metal roll is 50 ° C., and the nip pressure is 50 kg / cm. Soft calendar processing was performed under conditions.

(Second layer formation)
The prepared second layer coating solution is passed through a 150 mesh pole filter on both sides of the fine paper on which the first layer is formed, and then the dry mass per side is measured using a curtain coater. Each surface was applied so as to be 15 g / m ² and dried at a temperature of 70 ° C. and a wind speed of 10 m / sec for 1 minute to form a second layer. Further, soft calendering was performed on the formed second layer in the same manner as the first layer. The thickness of the formed second layer was 20.2 μm.
The ink jet recording medium of the present invention was produced as described above.

(Evaluation)
The following evaluation was performed about the obtained inkjet recording medium. The evaluation results are shown in Table 1 below.

-1. Cobb water absorption test
According to the water absorption test in accordance with JIS P8140, the Cobb water absorption on the surface of the first layer of the fine paper on which the first layer was formed (the amount of water permeation when contacted with water at 20 ° C. for 2 minutes g / M ² ) was measured.

-2. Second layer coatability test
The applicability when forming the second layer was evaluated according to the following evaluation criteria.
<Evaluation criteria>
A: The surface shape of the second layer was good.
B: Although cracks and coating unevenness were observed on the surface of the second layer, there was no practical problem.
C: There were many coating unevenness and repellency on the surface of the 2nd layer, and it was a level not worth printing evaluation.
D: The curtain film at the time of application was not stably formed (a sample for printing evaluation was not obtained).

-3. Absorption capacity test of diethylene glycol (DEG) of the second layer
1 mL of diethylene glycol was dropped on the ink receiving layer of a test piece obtained by cutting each recording medium so as to be 10 cm square, and after 30 seconds, the excess was wiped off, and the diethylene glycol absorption capacity (mL / mL) was determined from the weight difference before and after the dropping. m ² ) was determined.

-4. Curl test
The printed ink jet recording medium is cut to prepare a 50 mm × 5 mm size test piece, which is applied to the test piece so that water is 10 g / m ^{2 in} each of the MD and CD directions. Test Method No. 15-2: 2000 (Paper-Curl Test Method-Part 2) In accordance with the curl curvature measurement method defined in 15-2: 2000, the curl degree after standing for 8 hours at 23 ° C. and 50% RH is as follows. Evaluation was made according to criteria.
<Evaluation criteria>
A: The curl degree was less than 10.
B: The curl degree was 10 or more and less than 20.
C: Curling degree was 20 or more and less than 30.
D: Curling degree was 30 or more.

<Preparation of ink>
(1) Preparation of Cyan Pigment Ink C-Preparation of Pigment Dispersion-
A dispersion was prepared by stirring and mixing 10 g of cyanine blue A-22 (PB15: 3) manufactured by Dainichi Seika Co., Ltd., 10.0 g of the following low molecular weight dispersant, 4.0 g of glycerin, and 26 g of ion-exchanged water. Next, using an ultrasonic irradiation device (Vibra-cell VC-750, manufactured by SONICS, 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.

Apart from the pigment dispersion, the following compounds were weighed, stirred and mixed to prepare a mixture I.
・ Glycerin ... 5.0g
・ Diethylene glycol: 10.0 g
・ Orphine E1010 (manufactured by Nissin Chemical Industry) ・ ・ ・ 1.0g
・ Ion-exchanged water ... 11.0 g

This mixed liquid I was slowly dropped into 23.0 g of a stirred 44% SBR dispersion (polymer fine particles: 3% acrylic acid, Tg (glass transition temperature) 30 ° C.) and stirred and mixed to prepare mixed liquid II. did.
Next, this mixed liquid II was stirred and mixed while slowly dropping into the above-mentioned 20% by mass pigment dispersion to prepare 100 g of cyan pigment ink C (cyan ink). When the pH of the pigment ink C prepared as described above was measured using a pH meter WM-50EG manufactured by Toa DKK, the pH value was 8.5.

(2) Preparation of Magenta Pigment Ink M In the preparation of Pigment Ink C, Chromatic Jet Magenta DMQ (PR-122) manufactured by Ciba Specialty Chemicals was used in place of the pigment used in the preparation of Pigment Ink C. Prepared a magenta pigment ink M (magenta ink) in the same manner as the pigment ink C. When the pH of the pigment ink M prepared as described above 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 the preparation of Pigment Ink C, instead of using the pigment used for the preparation of Pigment Ink C, Ibarga Yellow GS (PY74) manufactured by Ciba Specialty Chemicals was used. Yellow pigment ink Y (yellow ink) was prepared in the same manner as the preparation of ink C. When the pH of the pigment ink Y prepared as described above 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 In the preparation of pigment ink C, a dispersion CAB-O-JETTM_200 (carbon black) manufactured by CABOT was used instead of the pigment dispersion used for the preparation of pigment ink C. Except for this, a black pigment ink K (black ink) was prepared in the same manner as in the preparation of pigment ink C. When the pH of the pigment ink K prepared as described above was measured with a pH meter WM-50EG manufactured by Toa DKK, the pH value was 8.5.

<Preparation of treatment liquid>
The treatment liquid was prepared by mixing the following components.
・ Phosphoric acid ... 10g
・ Glycerin 20g
・ Diethylene glycol ... 10g
・ Orphine E1010 (manufactured by Nissin Chemical Industry) ・ ・ ・ 1g
・ Ion-exchanged water ... 59g
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 1.0.

<Image formation and droplet ejection method and conditions>
Using the cyan pigment ink C, the magenta pigment ink M, the yellow pigment ink Y, the black pigment ink K, and the treatment liquid, a four-color single-pass image is formed using the apparatus shown in FIG. 3 under the following conditions. did. At this time, a gray scale and a character image were formed.

~ Head for treatment liquid 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 that applies at least one color ink to the processing liquid in advance at the drawing position 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)

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

Subsequently, the following droplet ejection test and tape peeling test were performed.
-5. Evaluation of droplet ejection
The gray scale and character image formed above were visually observed and evaluated according to the following evaluation criteria. The evaluation results are shown in Table 1 below.
<Evaluation criteria>
A: Image bleeding and color mixing were not observed, and “hawk” characters of 4 pt or less could be resolved.
B: No image blur or color mixing was observed, and resolution was possible up to 5 pt “hawk” characters.
C: Image blurring and color mixing were often observed, and the practicality was low.
D: Image bleeding, color mixing between colors was severe, and practicality was extremely low.

-6. Tape peeling test
After 3 hours of fixing and drying, a 12 mm wide mending tape (manufactured by 3M) was attached to the printed portion, and then the peeled state of the printed portion when the tape was peeled off was evaluated according to the following criteria. The evaluation results are shown in Table 1 below.
A: No peeling of the printed part was observed.
B: Although peeling of the printed part was observed, there was almost no influence on the image on the paper.
C: Peeling of the printed part was observed, and a part of the image on the paper remained.
D: The print part was severely peeled off, and almost no image on the paper remained.

(Example 2)
In Example 1, the addition amount of the 7.5% PVA105 aqueous solution was adjusted so that the solid content of PVA105 with respect to all pigments was 5% (the numerical value shown in Table 1), and the solid content of PVA145 with respect to all pigments was Other than changing the content ratio of PVA105 / PVA145 to the total pigment to 5% / 3% as shown in Table 1 by adjusting the addition amount of the 5% PVA145 aqueous solution to 3% (numerical values described in Table 1) Were produced in the same manner as in Example 1 and evaluated. The evaluation results are shown in Table 1 below.

(Example 3)
In Example 1, instead of each of PVA105 (average polymerization degree 500, Kuraray Co., Ltd.) and PVA145 (average polymerization degree 4500, Kuraray Co., Ltd.), PVA110 (average polymerization degree 1000, Kuraray Co., Ltd.) ) And PVA124 (average degree of polymerization 2400, manufactured by Kuraray Co., Ltd.) were used, and an inkjet recording medium was prepared and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1 below.

(Comparative Example 1)
(Preparation of second layer forming coating solution b)
2000 parts of water, kaolin (trade name: Kaoblite 90, manufactured by Shiraishi Calcium Co., Ltd.) 1500 parts, calcined kaolin (trade name: Kao Cal, manufactured by Shiraishi Calcium Co., Ltd.), and 40% sodium polyacrylate (product) Name: Aron T-50, 50 parts by Toagosei Co., Ltd.) was mixed and dispersed in water. In this pigment dispersion, 3200 parts of 5% PVA145 (manufactured by Kuraray Co., Ltd.) aqueous solution, 300 parts of 48% SBR (trade name: SN307, Nippon A & L), 10% Aerosol MA80 (manufactured by American Cyanamid Co., Ltd.) 200 parts of an aqueous solution and 200 parts of a 2% Lapisol A-90 (manufactured by NOF Corporation) solution were added to prepare a second layer forming coating solution b having a final solid content concentration of 27%.
The coating solution b was passed through a 150 mesh pole filter and then applied with a curtain coater so as to be 15 g / m ² , but the filter was clogged immediately and could not be applied.

(Comparative Example 2)
An inkjet recording medium was prepared and evaluated in the same manner as in Comparative Example 1 except that the coating liquid b was not passed through the 150 mesh pole filter in Comparative Example 1. The obtained coating film was cut or surface defects were caused. Detailed evaluation results are shown in Table 1 below.

(Comparative Example 3)
In Example 1, the addition amount of 7.5% PVA105 (average polymerization degree 500, manufactured by Kuraray Co., Ltd.) aqueous solution was changed to 2133 parts, the addition amount of 5% PVA145 aqueous solution was changed to 0 parts, and the solid content concentration was 35. % Inkjet recording media were prepared and evaluated in the same manner as in Example 1 except that the second layer-forming coating solution c was prepared. The evaluation results are shown in Table 1 below.

(Comparative Examples 4 and 5)
In Example 1, except that the coating amount of the second layer was changed to the amount described in Table 1, an ink jet recording medium was prepared and evaluated in the same manner as in Example 1. The evaluation results are shown in Table 1 below.

(Comparative Example 6)
In Comparative Example 1, an ink jet recording medium was prepared and evaluated in the same manner as Comparative Example 1 except that the coating amount of the first layer was changed to the amount shown in Table 1. The evaluation results are shown in Table 1 below.

(Comparative Example 7)
In Example 1, instead of 7.5% PVA105 (average polymerization degree 500, manufactured by Kuraray Co., Ltd.) aqueous solution, 7.5% PVA124 (average polymerization degree 2400, manufactured by Kuraray Co., Ltd.) aqueous solution was used. An ink jet recording medium was prepared and evaluated in the same manner as in Example 1 except that the coating amount of this layer was changed to the amount shown in Table 1. The evaluation results are shown in Table 1 below.

(Comparative Example 8)
In Example 1, a 5% PVA145 (average polymerization degree 4500, manufactured by Kuraray Co., Ltd.) aqueous solution was used instead of a 5% PVA110 (average polymerization degree 1000, manufactured by Kuraray Co., Ltd.) aqueous solution. An ink jet recording medium was prepared and evaluated in the same manner as in Example 1 except that the amount was changed to the amount shown in Table 1. The evaluation results are shown in Table 1 below.

  As shown in Table 1, the examples having the configuration of the present invention had no problem in all tests. On the other hand, at least one comparative example caused a problem.

It is a schematic block diagram which shows the structural example of the recording medium of this invention. It is explanatory drawing for demonstrating an example of the inkjet recording method which concerns on the 1st aspect using the recording medium of this invention. It is explanatory drawing for demonstrating an example of the inkjet recording method which concerns on the 2nd aspect using the recording medium of this invention. It is a schematic block diagram which shows the structure of the conventional recording medium.

Explanation of symbols

11 ... fine paper 12 ... solvent blocking layer (first layer)
13 ... Coat layer (second layer)
21 ... Base paper 22 ... Solvent absorption layer 100 ... Recording medium

Claims (10)

A base paper, a first layer containing a binder, a second layer containing kaolin, a polyvinyl alcohol having a polymerization degree of 1500 or more and 8000 or less and a polyvinyl alcohol having a polymerization degree of 100 or more and less than 1500 are sequentially laminated, The Cobb water absorption at a contact time of 120 seconds according to JIS P8140 on the surface of the first layer is 2.0 g / m ² or less, and the surface of the second layer is diethylene glycol having a contact time of 30 seconds. A recording medium having an absorption capacity of 2 mL / m ² or more and 8 mL / m ² or less. The recording medium according to claim 1, wherein the second layer further contains calcined kaolin. The recording medium according to claim 1 or 2, wherein the polymerization degree of the polyvinyl alcohol having a polymerization degree of 1500 or more and 8000 or less is 3000 or more and 8000 or less. The recording medium according to claim 1, wherein the second layer further contains a styrene-butadiene copolymer rubber. The recording medium according to claim 1, wherein the binder of the first layer is a latex of a thermoplastic resin. A first layer forming step of forming a first layer by applying a film-forming solution containing a binder on a base paper, and after adding a pigment dispersion containing kaolin to polyvinyl alcohol having a polymerization degree of 100 or more and less than 1500 And a second layer forming step of forming a second layer by applying a film-forming solution obtained by adding polyvinyl alcohol having a polymerization degree of 1500 or more and 8000 or less onto the first layer. Manufacturing method. The method for manufacturing a recording medium according to claim 6, wherein in the second layer forming step, the film forming liquid of the second layer is curtain-coated.   An ink drawing step of applying ink to the recording medium according to any one of claims 1 to 5 and drawing ink according to predetermined image data, and an ink solvent in the ink drawn ink And a drying removal step of drying and removing the ink.   A treatment liquid supply step of supplying a treatment liquid containing an acidic substance to the recording medium using the recording medium according to any one of claims 1 to 5, and applying ink to the recording medium, and predetermined The ink jet recording method according to claim 8, further comprising: an ink drawing step of drawing ink according to the image data that has been drawn, and a dry removal step of drying and removing the ink solvent in the recording medium on which the ink has been drawn. The ink jet recording method according to claim 9, wherein the acidic substance is a divalent or higher acid.