JP4082399B2 - Inkjet recording medium - Google Patents

Description

  The present invention relates to a recording medium that performs printing by an ink jet recording method, and more particularly to an ink jet recording medium having gloss on the surface of an ink receiving layer.

  An ink jet recording medium has a structure in which an ink receiving layer containing a porous pigment such as silica or alumina and a binder is provided on the surface of a support such as paper, and ink droplets are formed on the ink receiving layer. Has become established. With the remarkable progress of ink jet printers in recent years and the remarkable spread of digital cameras, the quality required for ink jet recording media is increasing year by year.

  By the way, the recording media of the ink jet recording system are roughly classified into a plain paper type having a texture similar to so-called high-quality paper and PPC paper and a coated paper type having an ink receiving layer. Further, the coated paper type recording medium is roughly classified into a gloss type having gloss in the ink receiving layer and a mat type having no gloss. In particular, in an inkjet recording medium having a gloss comparable to that of a conventional silver salt photograph, quality requirements are strict and technological development is actively being carried out.

The quality characteristics required for such a glossy inkjet recording medium include a high ink drying speed, a high print density, and no ink overflow or bleeding, which improve these characteristics. For this purpose, it is necessary to improve the ink receiving layer.
For example, Patent Document 1 reports a highly glossy record cast coated paper for ink jetting, in which colloidal silica is blended with synthetic silica. Further, the cast coating layer contains silica fine particles having an average primary particle size of 3 to 40 nm, secondary particle average particle size of 10 to 400 nm, and colloidal silica having an average particle size of 200 nm or less. The technique which performs is reported (for example, refer patent document 2).

On the other hand, in recent years, pigment inks using pigments as coloring materials are becoming popular due to the development of pigment dispersion technology. When an image is recorded with pigment ink, the storage stability is good, but when printing is performed on a conventional inkjet recording paper designed for dye ink, the color developability of the image is inferior, and the color material (pigment) is recorded on the recording paper. There was a problem of missing from the surface. In order to solve this problem, Patent Document 3 contains synthetic amorphous silica having an average particle diameter of 5 to 20 μm, polyvinyl alcohol having a saponification degree of 90.0 to 97.0 mol% and a polymerization degree of 1000 to 3500, Disclosed is a method in which an ink receiving layer having a compositional weight ratio of synthetic amorphous silica and polyvinyl alcohol of 100/100 to 100/20 is provided, and a good recorded image can be obtained by using dye ink or pigment ink. Has been.
In Patent Document 4, the roughness of the surface of the ink receiving layer is adjusted so that the 20 ° specular glossiness of the surface is 2 to 18% and the image definition glossiness is 20 or less. An ink jet recording medium having both compatibility and fixability is disclosed.

Japanese Patent Laid-Open No. 2-27487 JP 2000-85242 A JP 2003-94794 A JP 2002-321448 A

  However, in each of the above-described techniques, an ink jet recording paper having a high recorded image density has not been obtained even when either dye ink or pigment ink is used. In Patent Documents 1 and 2, although a highly glossy recording medium can be obtained, there is a problem that the printing density is low when printing with pigment ink. Further, in the ink jet recording sheet described in Patent Document 3, the color developability is not satisfactory in any case where printing is performed using dye ink or pigment ink. In Patent Document 4, a pigment having an average particle diameter of 1 μm or less is used to adjust the glossiness and surface roughness of the ink receiving layer in order to obtain a recording medium having good coloring and fixing properties of the pigment ink. In addition, there is a problem in color development and absorptivity at the time of printing, and since alumina hydrate is mainly used as a pigment, there is a problem in operability such as coating property due to poor stability of the coating liquid.

  Therefore, an object of the present invention is to provide an ink jet recording medium excellent in dye ink color developability, pigment ink color developability, and ink absorbability, and to improve operability.

As a result of various studies, the present inventors have used the following colloidal silica and synthetic amorphous silica as pigments, polyvinyl alcohol and casein as binders in the ink-receiving layer, and using a heated mirror-finished surface. The present inventors have found that the above problems can be solved by applying an aqueous solution having a function of coagulating polyvinyl alcohol and casein immediately before the gloss is imparted.
That is, the inkjet recording medium of the present invention is glossy by contacting at least one surface of the support with a heated mirror-finished surface containing a pigment and a binder and heated in a wet state. An ink jet recording medium having an ink-receiving layer provided with a pigment, wherein the pigment contains colloidal silica and synthetic amorphous silica, the binder contains polyvinyl alcohol and casein, and an ink. The receiving layer gives gloss by contacting the heated mirror surface immediately after applying an aqueous solution containing a compound having a function of coagulating polyvinyl alcohol and a compound having a function of coagulating casein to the surface of the ink receiving layer. has been Ri Na, the colloidal silica, a primary particle diameter of 23～55Nm, and the ratio of the secondary particle diameter to the primary particle diameter .5～2.5 is an inkjet recording medium characterized der Rukoto.
Further, it is preferable 75 ° specular gloss before Symbol ink receiving layer surface is 50% or more.

The present invention also relates to a method for producing an ink jet recording medium in which a glossy ink receiving layer is formed on at least one surface of a support , wherein the primary particle diameter is 23 to 55 nm as a pigment. Supports ink-receiving layer coating liquid containing colloidal silica and synthetic amorphous silica with a ratio of secondary particle diameter to diameter of 1.5 to 2.5, and polyvinyl alcohol and casein as binders After coating on at least one surface of the body to provide a coating layer, the coating layer has a function of coagulating polyvinyl alcohol and a compound having a function of coagulating polyvinyl alcohol while the coating layer is in a dry or wet state. An aqueous solution containing the compound is applied to the surface of the coating layer, and immediately after the aqueous solution is applied, the surface of the coating layer and the heated mirror-finished surface are brought into contact with each other to obtain a gloss It is a manufacturing method of the ink-jet recording medium and forming an ink-receiving layer having.

  According to the present invention, it is possible to obtain an ink jet recording medium having a high recorded image density (coloring property) and high ink absorptivity regardless of whether dye ink or pigment ink is used. In addition, it is possible to obtain an ink jet recording medium excellent in glossiness and to remarkably improve the operability in cast coating.

Embodiments of the present invention will be described below. In the ink jet recording medium of the present invention, an ink receiving layer containing a pigment and a binder is provided on at least one surface of a support.
(Support)
Any support can be used as long as it is in the form of a sheet, but a support having air permeability is preferable. For example, paper such as coated paper and uncoated paper is preferably used. The raw material pulp of the paper includes chemical pulp (coniferous bleached or unbleached kraft pulp, hardwood bleached or unbleached kraft pulp, etc.), mechanical pulp (ground pulp, thermomechanical pulp, chemisermomechanical pulp, etc.), deinking Pulp or the like can be used alone or mixed at an arbitrary ratio. The pH of the paper may be acidic, neutral or alkaline. Further, in order to improve the opacity, it is preferable to contain a filler in the paper, but this filler is hydrated silicic acid, white carbon, talc, kaolin, clay, calcium carbonate, titanium oxide, synthetic resin fine particles, etc. It can be appropriately selected from known fillers. From the viewpoint of operability, the air permeability of the paper is preferably 1000 seconds or less, and from the viewpoint of coating properties, the Steecht size of the base paper is preferably 5 seconds or more.

(Pigment of ink receiving layer)
As the pigment in the present invention, a pigment containing synthetic amorphous silica and colloidal silica described in detail below is used as an essential component.
Synthetic amorphous silica can be roughly classified into wet method silica and gas phase method silica depending on the production method. Synthetic amorphous silica produced by a wet method is inferior to gas phase method silica in terms of pigment transparency, but is excellent in paint stability when used in combination with polyvinyl alcohol. Furthermore, the dispersibility is better than that of vapor-phase process silica having no internal voids, and the paint concentration can be increased. Therefore, it is considered that the pigment ratio in the ink receiving layer can be increased and the absorbability of the ink receiving layer can be increased, so that the ink absorbability can be improved and the color developability of the dye ink can be improved.
From the viewpoint of obtaining a high gloss feeling, the preferred secondary particle diameter of the synthetic amorphous silica is 1 to 5 μm. Moreover, it is preferable that a BET specific surface area is 150-500 m < ² > / g.

The colloidal silica used in the present invention is a synthetic silica having a primary particle diameter of about several nanometers to 100 nm synthesized by a wet method, and is agglomerated into nonspherical secondary particles. Cases are also included. The colloidal silica used this time preferably has a primary particle size of 23 to 55 nm. More preferably from 23 ~40nm. When the primary particle size is less than 23 nm, the ink color developability is greatly reduced when printing is performed with an ink jet printer using pigment ink. On the other hand, when the primary particle diameter exceeds 55 nm, the voids between the particles increase and the ink absorbability of the ink receiving layer is improved, but the opacity increases, so that the coloring property of the dye ink during ink jet recording is increased. descend.

  In the present invention, the colloidal silica is more preferably in the form of an association. By containing the associated colloidal silica in the ink receiving layer, the color developability of the pigment ink can be greatly improved. Spherical (non-secondary aggregated) and chain colloidal silica tends to have a lower color developability of the dye ink as compared to associated colloidal silica. The shape of the colloidal silica described above can be observed with a microscope (such as SEM). The primary particle size of colloidal silica can be measured by the BET method and the secondary particle size can be measured by the dynamic light scattering method. Here, the chain colloidal silica is a shape in which several to a dozen or more primary particles are connected in a chain shape, and the ratio of the secondary particles to the primary particles is larger than 2.5. Colloidal silica in which several primary particles are combined and the ratio of secondary particles to primary particles is 1.5 to 2.5. When associating colloidal silica is usually observed with a microscope, a large number of spherical single colloidal silica (primary particles) are observed. For convenience, this is expressed as a peanut shape. In the present invention, two or more kinds of colloidal silica having different primary particles and shapes can be used in combination.

  The peanut-shaped colloidal silica is synthesized by sol-gel method using alkoxysilane as a raw material, and the primary particle size (BET method particle size) and secondary particle size (dynamic light scattering method particle size) are controlled according to the synthesis conditions. It is preferable to do. As such colloidal silica, a trade name Quatron manufactured by Fuso Chemical Industry Co., Ltd. can be raised.

The blending ratio of the synthetic amorphous silica and the colloidal silica in the ink receiving layer is preferably such that the value of (colloidal silica) / (synthetic amorphous silica) is in the range of 30/70 to 75/25. More preferably, it is in the range of 50/50 to 70/30.
When the blending ratio of colloidal silica is small, there is a tendency that the effect of improving color developability when ink jet printing is performed with pigment ink. Moreover, when there are many compounding quantities, there exists a tendency for the coloring property of dye ink to fall, and also the operativity at the time of coating may fall.

  The pigment further includes other pigments, such as aluminum hydroxide, alumina (α-type crystal alumina, θ-type crystal alumina, γ-type crystal), as long as ink absorbability, color developability, and glossiness are not impaired. Alumina, etc.) or alumina hydrates (alumina sol, colloidal alumina, pseudoboehmite, etc.), kaolin, talc, calcium carbonate, titanium dioxide, clay, zinc oxide, etc. may be used in combination. It is preferable to set it as 10 mass% or less with respect to the total pigment of a layer.

(Binder for ink receiving layer)
As the binder in the present invention, polyvinyl alcohol and casein are essential components. By containing polyvinyl alcohol, the ink receiving layer is excellent in ink color development and ink absorbability. In the present invention, any type of polyvinyl alcohol can be used, but the saponification degree is preferably less than 98%. A saponification degree of less than 98% is called partially saponified polyvinyl alcohol or intermediate saponified polyvinyl alcohol. As the saponification degree is lower, the ink absorbability tends to be improved. This is presumably because the lower the degree of saponification, the higher the hydrophilicity of polyvinyl alcohol and the better the ink absorption.

Further, when the degree of polymerization of polyvinyl alcohol is high, the ink absorbability tends to be poor when printing with a dye ink. From the viewpoint of improving ink absorbability, the degree of polymerization is preferably less than 2000. This is presumably because when the degree of polymerization is high, the solubility of polyvinyl alcohol is poor when it comes into contact with the ink solvent. On the other hand, the higher the degree of polymerization of polyvinyl alcohol, the higher the print density of the pigment ink tends to be. Therefore, the degree of polymerization is preferably 2000 or more from the viewpoint of improving the color developability of the pigment ink. The reason for this is that as the degree of polymerization increases, the binder tends to remain on the surface of the coating layer, and therefore cracks in the coating layer are reduced. It is considered that when the cracks are reduced, the color pigment in the ink tends to stay on the surface, and the color developability (print density) is improved.
In addition, when casein is blended in the ink receiving layer, the coating property of the coating liquid to be the ink receiving layer is improved, and good gloss is easily obtained even with a small amount of binder. In addition, when the amount of the binder in the ink receiving layer is small, the voids in the ink receiving layer are increased, and it is considered that the ink absorbability when printing by inkjet is improved.

  Furthermore, in the present invention, other polymer compounds can be used in combination as a binder as long as the color developability, absorbency and glossiness are not impaired. For example, starches such as starch, oxidized starch and esterified starch, cellulose derivatives such as carboxymethylcellulose and hydroxyethylcellulose, polyvinylpyrrolidone, gelatin, soy protein, styrene-acrylic resin and its derivatives, styrene-butadiene resin, acrylic resin, acetic acid Vinyl resin, vinyl chloride resin, urethane resin, urea resin, alkyd resin, and derivatives thereof can be used. The blending amount of the binder is preferably 5 to 30 parts by weight with respect to 100 parts by weight of the pigment, but is not particularly limited as long as the necessary coating layer strength is obtained. When the blending amount of the binder increases, the color developability tends to be improved when ink jet recording is performed with the pigment ink, but the ink absorbability tends to decrease.

  The ink receiving layer contains the above-described pigment and binder, but other components such as a thickener, an antifoaming agent, an antifoaming agent, a pigment dispersant, a release agent, a foaming agent, a pH adjusting agent, and a surface. Sizing agent, coloring dye, coloring pigment, fluorescent dye, ultraviolet absorber, antioxidant, light stabilizer, preservative, water resistance agent, dye fixing agent, surfactant, wet paper strength enhancer, water retention agent, cation A functional polymer electrolyte or the like can be appropriately added within a range not impairing the effects of the present invention.

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

The coating amount of the ink receiving layer can be arbitrarily adjusted within the range where the surface of the support is covered and sufficient ink absorbability is obtained, but from the viewpoint of achieving both color developability and ink absorbency, It is preferably 5 to 30 g / m ² in terms of solid content.
In the present invention, when a large coating amount of the ink receiving layer is required, the ink receiving layer can be multi-layered. Further, an undercoat layer having various functions such as ink absorptivity and adhesiveness may be provided between the support and the ink receiving layer. Further, a back coat layer having various functions such as ink absorbability, writing property, printer printability and the like may be further provided on the side opposite to the surface on which the ink receiving layer is provided.

  In the present invention, high color developability and ink absorbency can be achieved even in an inkjet recording medium having a 75 ° specular gloss of 50% or more and a gloss comparable to a silver salt photograph.

  In the present invention, as a method of imparting gloss to the surface of the ink jet receiving layer, a method of imparting gloss by bringing the ink receiving layer into contact with a heated mirror-finished surface in a wet state is used, but the manufacturing cost is low. It is preferable to manufacture from the above by the cast coat method using a cast coater. The cast coating method is a method in which a coating liquid mainly composed of a pigment and a binder is applied onto a base paper to provide a coating layer, and the coating layer is gloss-finished using a cast drum. The gloss coating layer becomes the ink receiving layer.

  The cast coating method includes (1) a wet casting method (direct method) in which a coating layer is pressed onto a mirror-finished heating drum while the coating layer is wet, and (2) a wet coating layer is once dried. Alternatively, a semi-dried, rewetting method that is swollen and plasticized with a re-wetting solution, and press-dried on a mirror-finished heating drum and then dried. There are generally known three types of gelation cast methods (coagulation methods) in which pressure is bonded to the substrate and dried. The principle of each method is the same in that the wet coating layer is pressed against the mirror-finished surface to give gloss to the coating layer surface.

In the present invention, an ink receiving layer containing a compound having a function of coagulating polyvinyl alcohol and a compound having a function of coagulating casein immediately before the gloss is imparted to the ink receiving layer using a mirror-finished surface. Apply to layer surface.
Examples of the compound having an action of coagulating polyvinyl alcohol include boric acid and borates. Examples of borates include, but are not limited to, borax, orthoborate, diborate, metaborate, pentaborate, and octaborate. From the viewpoints of cost and availability, borax is preferably used.

Moreover, by mixing and using boric acid and borate, it becomes easy to make the hardness at the time of solidification moderate, and a good glossiness can be imparted to the ink receiving layer. The mixing ratio of borate and boric acid is particularly preferably between 0.25 / 1 and 2/1. When the borate / boric acid compounding ratio is less than 0.25 / 1, the boric acid ratio is too high, so that the solidification of the polyvinyl alcohol in the recording layer is too soft. In some cases, a recording layer in a good wet state cannot be obtained. On the other hand, when the borate / boric acid compounding ratio exceeds 2/1, the solidification of the polyvinyl alcohol in the recording layer becomes hard, so the glossiness of the cast-coated paper surface is lowered and gloss unevenness occurs. Sometimes.
The concentration of borate and boric acid in the aqueous solution can be adjusted as needed. When the concentration of borate and boric acid in the aqueous solution is increased, the coagulation of polyvinyl alcohol is increased and the gloss tends to be inferior. On the other hand, when the concentration is high, boric acid is likely to be precipitated in the treatment liquid, so that the stability of the aqueous solution is deteriorated. Preferably it is 1-5 mass%.

  Examples of the compound having the action of coagulating casein include acids such as formic acid, acetic acid, citric acid, tartaric acid, lactic acid, hydrochloric acid and sulfuric acid, and various salts such as calcium, zinc and magnesium. In particular, when formate is used, casein is easily coagulated even in a small amount. Moreover, since the salt containing calcium, zinc, magnesium or the like described above may deteriorate the ink colorability, the concentration of the salt in the aqueous solution is preferably 1 to 7% by mass. In addition, as long as it is a compound which volatilizes in the drying process and does not remain in the ink receiving layer, such as ammonium formate, it can be incorporated in the aqueous solution up to about 10% by mass.

As a method of imparting gloss using the aqueous solution, for example, the following method is performed. First, a coating liquid to be an ink receiving layer is applied to a support. Next, the aqueous solution is applied to the coating layer to make the coating layer wet. Then, the wet coating layer is pressure-bonded to a heated mirror-finished surface and dried to form an ink receiving layer, and gloss is imparted to the surface. The coating layer at the time of applying the aqueous solution may be in a wet state or in a dry state, but in particular when it is in a wet state, it is easy to copy the mirror-finished surface, and the coating layer surface has a minute amount. Since the unevenness can be reduced, it is easy to give the obtained ink-receiving layer glossiness equivalent to that of a silver salt photograph.
Examples of the method for applying the aqueous solution include, but are not limited to, a roll, a spray, and a curtain method.

When the aqueous solution is applied while the coating layer is wet, it corresponds to the gelation cast method (coagulation method), and when the aqueous solution is applied to the coating layer in a dry state, it corresponds to the rewetting method. In the present invention, a method of applying the aqueous solution while the coating layer is in a wet state (gelation cast method (coagulation method)) in that it is possible to impart a surface feeling and gloss comparable to a silver salt photograph. It is preferable to form an ink receiving layer using
Next, the case where the gelation cast method is used will be described. In this cast coating method, after the coating layer is applied, the undried coating layer is gelled with a coagulating liquid and then pressed and dried on a heated mirror-finished surface. If the coating layer is in a dry state when the liquid is applied, it is difficult to copy the surface of the mirror drum, and the surface of the ink receiving layer obtained has a lot of fine irregularities, making it difficult to obtain a glossy feeling comparable to that of a silver salt photograph.

  Further, a release agent can be added to the aqueous solution containing the ink receiving layer coating liquid and / or the coagulant as necessary. The melting point of the release agent is preferably 90 to 150 ° C, and particularly preferably 95 to 120 ° C. In the above temperature range, since the melting point of the release agent is substantially equal to the temperature of the mirror finish surface, the ability as a release agent is maximized. The release agent is not particularly limited as long as it has the above characteristics, but it is preferable to use a polyethylene wax emulsion.

As the ink used in the ink jet recording method of the present invention, a dye for forming an image and a liquid medium for dissolving or dispersing the dye are essential components, and if necessary, various dispersants, surfactants, It is adjusted by adding a viscosity adjuster, a specific resistance adjuster, a pH adjuster, an antifungal agent, a recording agent dissolution or dispersion stabilizer, and the like.
Examples of the recording agent used in the ink include direct dyes, acid dyes, basic dyes, reactive dyes, food dyes, disperse dyes, oil-based dyes, and various pigments. be able to. The content of such a coloring matter is determined depending on the type of liquid medium component, characteristics required for the ink, etc., but in the case of the ink in the present invention, the blending in the conventional ink, that is, There is no problem in particular when it is used in a proportion of about 0.1 to 20% by weight.

  Examples of the solvent for the ink used in the present invention include water and various water-soluble organic solvents such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, and isobutyl alcohol. Alkyl alcohols, ketones or ketone alcohols such as acetone and diacetone alcohol, polyalkylene glycols such as polyethylene glycol and polypropylene glycol, ethylene glycol, propylene glycol, butylene glycol, triethylene glycol, thiodiglycol and hexylene Alkylene glycols having 2 to 6 alkylene groups such as glycol and diethylene glycol, amides such as dimethylformamide, ethers such as tetrahydrofuran, glycerin, Chi glycol methyl ether, diethylene glycol methyl (ethyl) ether, such as lower alkyl ethers of polyhydric alcohols such as triethylene glycol monomethyl ether.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in full detail, this invention is not limited by this. Unless otherwise specified, “part” and “%” described below represent “part by mass” and “% by mass”, respectively.

<Example 1>
Pulp slurry consisting of 100 parts hardwood bleached kraft pulp (L-BKP) with a beating degree of 285 ml 10 parts by weight of talc, 1.0 part by weight of aluminum sulfate, 0.1 part by weight of synthetic sizing agent, 0.02 part by weight of yield improver When paper was added to the support with added parts, starch was coated on both sides so that the solid content per side was 2.5 g / m ² to obtain a base paper having a basis weight of 170 g / m ² . The base paper was coated with the following underlayer coating solution with a blade coater so that the coating amount was 8 g / m ² on one side and blown and dried at 140 ° C. Next, 20 g / m ^{2 of} coating solution A for casting was applied to the surface coated with the under layer with a roll coater, and the coating layer was solidified using the coagulating solution (1) while it was in a wet state. Then, it was pressed against a mirror-finished surface heated through a press roll, and the mirror surface was copied to obtain an ink jet recording medium of 198 g / m ² .

<Under layer coating solution>
As a pigment, 100 parts of synthetic silica (Fine Seal X-37: manufactured by Tokuyama Co., Ltd.), 5 parts of latex (LX438C: trade name manufactured by Sumitomo Chemical Co., Ltd.) and polyvinyl alcohol (PVA117: manufactured by Kuraray Co., Ltd.) Product name) 24 parts, 5 parts of sizing agent (Polymalon 360: trade name of Arakawa Chemical Co., Ltd.), 5 parts of ink fixing agent (Polyfix 700: trade name of Showa Polymer Co., Ltd.) % Aqueous coating solution was prepared.

<Cast layer coating liquid A>
As a pigment, 70 parts of colloidal silica having an average primary particle diameter of 23 nm and a secondary particle / primary particle diameter ratio of 2.2 (Quarton PL-2: a trade name manufactured by Fuso Chemical Industry Co., Ltd.) and a specific surface area of 279 m. Polyvinyl alcohol (PVA224: Kuraray Co., Ltd.) having a polymerization degree of 2400 using 30 parts of precipitated silica (Fine Seal X-37: manufactured by Tokuyama Co., Ltd.) with an average particle size of 2.8 μm at ² / g. ), 5 parts of casein, 10 parts of urethane (Oleister UD-170N: trade name, manufactured by Mitsui Chemicals) and 0.2 part of antifoaming agent were blended to prepare a coating solution having a concentration of 20%. .
<Coagulation liquid (1)>
A coagulating liquid was prepared by blending 4% boric acid (H ₃ BO ₃ ), 5% ammonium formate, and 0.2% mold release agent (FL-48C: manufactured by Toho Chemical Industry Co., Ltd.).

<Example 2>
In Example 1, the pigment mixing ratio of the coating layer coating liquid A was colloidal silica having an average primary particle diameter of 23 nm and a secondary particle / primary particle diameter ratio of 2.2 (Quarton PL-2: Fuso Chemical). Example 1 except that 50 parts of a trade name manufactured by Kogyo Co., Ltd., 50 parts of precipitated silica (Fine Seal X-37: manufactured by Tokuyama Co., Ltd.) and boric acid in the coagulation liquid (1) were adjusted to 2%. In the same manner, an ink jet recording medium was obtained.

<Example 3>
An ink jet recording medium was obtained in the same manner as in Example 1 except that boric acid in the coagulation liquid (1) was changed to 2% borax (Na ₂ B ₄ O).

<Example 4>
Example 1 was the same as Example 1 except that the urethane in the coating layer coating solution was not blended, the casein was 7.5 parts, and the ammonium formate in the coagulation solution (1) was changed to 5% calcium formate. Thus, an ink jet recording medium was obtained.

<Example 5>
In Example 1, the pigment in the cast layer coating solution was colloidal silica having an average primary particle size of 23 nm and a secondary particle / primary particle size ratio of 2.2 (Quarton PL-2: manufactured by Fuso Chemical Industries, Ltd.). ), 70 parts of precipitated silica (Fine Seal X-60: manufactured by Tokuyama Corporation) having a specific surface area of 301 m ² / g and an average particle size of 6.2 μm, and a polymerization degree of 2400 polyvinyl An ink jet recording medium was obtained in the same manner as in Example 1 except that 10 parts of alcohol (PVA224: trade name of Kuraray Co., Ltd.) was used.

<Example 6>
In Example 1, the pigment in the cast layer coating solution was colloidal silica having an average primary particle size of 52 nm and a secondary particle / primary particle size ratio of 2.2 (Quarton PL-5: manufactured by Fuso Chemical Industries, Ltd.). Product name) was 70 parts, and the specific surface area was 279 m ² / g and the average particle size was 2.8 μm, and the precipitation method silica (Fine Seal X-37: manufactured by Tokuyama Corporation) was changed to 30 parts. In the same manner, an ink jet recording medium was obtained.

< Comparative Example 7>
In Example 1, the pigment in the coating layer coating solution was colloidal silica having an average primary particle size of 70 nm and a secondary particle / primary particle size ratio of 1.7 (Quarton PL-7: manufactured by Fuso Chemical Industries, Ltd.). Product name) was 70 parts, and the specific surface area was 279 m ² / g and the average particle diameter was 2.8 μm, and precipitated silica (Fine Seal X-37: manufactured by Tokuyama Corporation) was changed to 30 parts. In the same manner, an ink jet recording medium was obtained.

< Comparative Example 8>
In Example 7, an ink jet recording medium was obtained in the same manner as in Example 1 except that the undercoat layer was not provided and the urethane in the cast coating layer was changed to 5 parts and cast coating was performed.

< Comparative Example 9>
In Example 1, the pigment in the cast layer coating solution is a tufted colloidal silica (Snowtex ST-HS-M20) having an average primary particle size of 25 nm and a secondary particle / primary particle size ratio of 11.1. : 70 parts by name (trade name manufactured by Nissan Chemical Industries), and 30 parts by precipitation method silica (Fine Seal X-37: manufactured by Tokuyama Corporation) having a specific surface area of 279 m ² / g and an average particle size of 2.8 μm. Except for the above, an ink jet recording medium was obtained in the same manner as in Example 1.

< Comparative Example 10>
Inkjet recording was performed in the same manner as in Example 1 except that colloidal silica was changed to spherical colloidal silica (Snowtex ST-30: trade name manufactured by Nissan Chemical Industries, Ltd.) having a primary particle size of 10 to 20 nm. A recording medium was obtained.

<Comparative Example 1>
An ink jet recording medium was obtained in the same manner as in Example 1 except that boric acid of the coagulating liquid (1) was not added.
<Comparative example 2>
An ink jet recording medium was obtained in the same manner as Example 1 except that the coagulating liquid (1) was 5% calcium formate and 0.2% release agent (FL-48C: manufactured by Toho Chemical Industry Co., Ltd.).

<Comparative Example 3>
An ink jet recording medium was obtained in the same manner as in Comparative Example 2 except that the coagulating liquid (1) was changed to 4% borax and 0.2% release agent (FL-48C: manufactured by Toho Chemical Co., Ltd.).
<Comparative Example 4>
In Example 1, an ink jet recording medium was obtained in the same manner as in Example 1 except that casein as a binder in the coating layer coating solution was not used.
<Comparative Example 5>
In Example 1, an ink jet recording medium was obtained in the same manner as in Example 1 except that PVA as a binder in the cast layer coating solution was not used.
<Comparative Example 6>
In Example 1, colloidal silica, which is a pigment in the coating layer coating solution, is not blended, and the pigment is 100 parts of precipitated silica (Fine Seal X-37: manufactured by Tokuyama Corporation). In the same manner, an ink jet recording medium was obtained.

The cast coating operability, glossiness, and inkjet recording test of the inkjet recording papers obtained in Examples 1 to 6 and Comparative Examples 1 to 10 were performed by the following methods. The results are summarized in Tables 1 and 2.
(1) Operability The dirt on the cast drum surface was visually evaluated when coating with a cast coater. ○: The cast drum surface was not dirty. △: The cast drum surface was slightly clouded. (2) Glossiness with part of the layer adhered The glossiness of the cast coated paper surface was evaluated according to the following criteria.
○: 75 degree specular gloss is 50% or more and image definition is 40% or more Δ: 75 degree specular gloss is 50% or more and image definition is 20% or more and less than 40% ×: 75 With a specular gloss of 50% or less ・ Measurement of 75-degree specular gloss according to JIS P8142: 75-degree specular gloss using a gloss meter (Murakami Color Research Laboratory, True GLOSS GM-26PRO) The degree was measured.
Image sharpness: Measured according to JIS K7105 using a image clarity measuring device (model number: ICM-1DP, manufactured by Suga Test Instruments Co., Ltd.). The MD direction of the paper was measured under the conditions of a measurement angle of 60 degrees and a comb width of 2 mm.

(3) Inkjet recording test In the recording test, an ink jet printer using dye ink (PM-970C: trade name of Epson Corporation) and an ink jet printer using pigment ink (PX-V700: trade name of Epson Corporation) A predetermined pattern was recorded using and evaluated according to the following criteria.
a. Ink absorption (bleeding)
Bleeding was visually evaluated at the boundary between the red and green mixed colors.
○: The color boundary portion is clearly separated. △: The color boundary portion is slightly blurred, and the degree of bleeding is relatively large. ×: The color boundary portion is very blurred. b, Vividness Vividness of the recorded image portion was visually evaluated.
◎: Very vivid ○: Vivid △: Slightly inferior x: Invisible

(4) Particle size measurement of colloidal silica a) Measurement of primary particle size The specific surface area (nitrogen adsorption method) of the sample was measured, and the primary particle size was determined by calculation according to the following formula (1).
d = 6000 / (ρ × S) (1)
In the formula (1), d: primary particle diameter (nm), ρ: silica density (= 2.2 g / m ³ ), and S: specific surface area S (m ² / g).
b) Measurement of secondary particle size
Measurement was performed using ZETASIZER 3000HSA manufactured by MALVERN INSTRUMENTS.

As is clear from Tables 1 and 2, the inkjet recording papers of the present invention of Examples 1 to 6 were highly evaluated in all of operability, glossiness, and printability. In Comparative Examples 7 to 8 having a large primary particle size of colloidal silica, the vividness of the dye ink was slightly inferior, and in Comparative Example 8 in which no under layer was provided, the absorbability of the dye ink was slightly inferior. In Comparative Example 10 using spherical colloidal silica, the absorbability of the dye and the pigment ink was slightly inferior.
On the other hand, in Comparative Example 1 using only ammonium formate as the coagulant, the operability and glossiness were slightly inferior, and the absorbability of the dye ink was inferior. Further, when only calcium formate was used as a coagulant, coagulation was insufficient and a good recording medium could not be obtained. In Comparative Example 3 using only borax as the coagulant, the operability and glossiness were slightly inferior, and the pigment ink was inferior in vividness. The comparative example 4 which does not mix | blend casein as a binder was a little inferior in operativity and glossiness, and was not vivid with the pigment ink. Further, in Comparative Example 5 in which no PVA was blended, the operability and glossiness were slightly inferior, and there was no vividness in dye and pigment printing. In Comparative Example 6 in which no colloidal silica was blended, the operability was slightly inferior, the glossiness was inferior, and it was subject to vividness with the pigment ink.

In addition, the shape of the colloidal silica in a table | surface is classified and representing the aggregation state of the colloidal silica observed with a microscope for convenience, and "peanut shape" is like a peanut in which about two primary particles are combined. In addition, “tufted” means that the bunches of grapes are observed, and “spherical” means that spherical particles are observed as independent.

Claims (3)

Ink jet having an ink-receiving layer containing a pigment and a binder on at least one surface of a support and having a gloss imparted by contact with a heated mirror-finished surface heated in a wet state The pigment contains colloidal silica and synthetic amorphous silica, the binder contains polyvinyl alcohol and casein, and the ink receiving layer has a function of coagulating polyvinyl alcohol. compound and Ri Na and the gloss is imparted by an aqueous solution containing a compound having an action of coagulating the casein into contact with the heated mirror surface immediately after coating the ink receiving layer surface, wherein the colloidal silica, primary particles diameter in 23～55Nm, and the ratio of the secondary particle diameter to the primary particle diameter and wherein 1.5 to 2.5 der Rukoto inkjet Use a recording medium. The inkjet recording medium according to claim 1 , wherein the 75 ° specular gloss of the surface of the ink receiving layer is 50% or more. A method for producing an inkjet recording medium, wherein a glossy ink-receiving layer is formed on at least one surface of a support, wherein the primary particle diameter is 23 to 55 nm as a pigment, and the secondary particle diameter relative to the primary particle diameter A coating liquid for an ink receiving layer containing colloidal silica having a ratio of 1.5 to 2.5 and synthetic amorphous silica and polyvinyl alcohol and casein as a binder is used as at least one of the supports. After coating on the surface and providing a coating layer, the coating layer contains a compound having a function of coagulating polyvinyl alcohol and a compound having a function of coagulating casein while the coating layer is in a dry state or a wet state. An aqueous solution is applied to the surface of the coating layer, and immediately after the aqueous solution is applied, the surface of the coating layer and the heated mirror-finished surface are brought into contact with each other to give a glossy ink Method of manufacturing an ink jet recording medium and forming a physical layer.