JPH10114143A - Ink jet recording paper - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink jet recording paper excellent in writing performance and absorbing ink quickly without spreading a dot. SOLUTION: In an ink jet recording paper where a coating layer is provided on a base paper, the coating layer contains 10-60 pts.wt. of synthetic amorphous silica produced through gelation, and 40-90 pts.wt. of synthetic amorphous silica produced through precipitation. The synthetic amorphous silica produced through qelation has mean grain size of 2.0-10.0μm while the synthetic amorphous silica produced through precipitation has mean grain size of 3.0-8.0μm. Preferably, the difference of mean grain size is at least 1.0μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet recording sheet, and more particularly to an ink jet recording sheet having a high ink absorbency, a small spread of dots, and a good writing property.

[0002]

2. Description of the Related Art The ink jet recording system has advantages such as easy multi-color recording, relatively high recording speed, and recording of large plates. On the other hand, nozzle clogging and maintenance, which has been a problem in the past, have been improved in terms of both ink and equipment, and are now widely used in various fields such as various printers, facsimiles, and computer terminals. Is rapidly spreading.

In the color ink jet process, cyan (C), cyan (C),
A water-based ink liquid of each color of magenta (M), yellow (Y), and black (K) is ejected toward the inkjet recording paper. Ink-jet recording paper, in the case of a single-color solid printing only by each of the above colors, it is only necessary to absorb only one kind of the aqueous ink liquid of each of the above colors,
For example, in the case of mixed color solid printing using green (G) or the like, it is necessary to absorb two or more types of aqueous ink liquids of the respective colors. For this reason, the ink jet recording paper used in the color ink jet process is required to have excellent ink absorbency.

Conventionally, in order to improve the ink absorbency, a support having improved absorbency to vehicles such as water and solvents by adjusting the height of the bulk, the air permeability, the size and the like has been provided. Paper has been proposed. However, in the case of this conventional paper, there is a problem that the manner in which ink droplets spread on the paper surface is irregular, ink flow occurs, and the color density tends to decrease. If the ink absorptivity is not sufficient, the spread of the ink dots is too large to cause ink bleeding, and the ink bleeds also to occur in the mixed color solid printing portion, and it is not possible to obtain a high-density and clear color image. is there. On the other hand, even if it has excellent ink absorbency, it cannot be said that it is a high-quality ink jet recording paper because of poor surface properties and poor writability. It is important that the ink jet recording paper has excellent surface properties and good writing properties.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and achieve the following objects. That is, an object of the present invention is to provide an ink jet recording paper having a high ink absorbency, a small spread of dots, and a good writability.

[0006]

The above object has been achieved by the following means. That is, (1) In an ink jet recording paper having a coating layer provided on a base paper, the coating layer was formed by 10 to 60 parts by weight of synthetic amorphous silica manufactured by a gelling method, and manufactured by a precipitation method. An ink jet recording paper comprising 40 to 90 parts by weight of synthetic amorphous silica. (2) The average particle diameter of the synthetic amorphous silica produced by the gelling method is 2.0 to 10.0 μm, and the average particle diameter of the synthetic amorphous silica produced by the precipitation method is 3.0 to 10.0. 8.0 μm, and the difference between the average particle diameter of the synthetic amorphous silica produced by the gelation method and the average particle diameter of the synthetic amorphous silica produced by the precipitation method is at least 1.0 μm. The said (1)
2. The ink jet recording paper according to item 1. (3) The inkjet recording paper according to (1) or (2), wherein the coating layer has a Beck smoothness of 20 to 80 seconds.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The ink jet recording paper of the present invention is provided with a coating layer on a base paper. LB as base paper
KP, NBPK and the like mainly composed of wood pulp may be mentioned. The base paper may further contain a synthetic pulp, a synthetic fiber or the like as needed. The freeness after beating is 250 to 450 cc (CSF).
Is preferred. The base paper in the present invention may contain a filler, a sizing agent, a paper strength agent, a fixing agent, and the like, if necessary.

[0008] Examples of the filler include clay, talc, TiO ₂ , CaCO ₃ , BaSO _{4 and the} like. The content of the filler is usually 0 to pulp.
-30 parts by weight. As the sizing agent, for example,
Rosin, alkenyl succinate, stearate, alkyl ketene dimer, alkenyl succinic anhydride and the like can be mentioned. Examples of the paper strength agent include starch, gelatin, CMC, polyacrylamide and the like.
Examples of the fixing agent include aluminum sulfate, aluminum chloride, polyamide polyamine epichlorohydrin and the like.

The basis weight of the base paper is usually 30 to 250 g.
/ M ² , preferably 5 to 150 g / m ² .
The thickness of the base paper is usually from 30 to 250 μm, preferably from 50 to 150 μm. The whiteness (hunter) of the base paper is preferably 70% or more. The stiffness (Taber) of the base paper is preferably from 1 to 29 g. The water absorption of the base paper is preferably from 10 to 30 g / m ^{2 according} to JIS-P-8140. If the water absorbency is less than 10 g / m ² , ink flow may easily occur. On the other hand, if it exceeds 30 g / m ² , white spots may easily occur.

The coating layer is composed of a synthetic amorphous silica produced by a gelling method (hereinafter sometimes abbreviated as “gelling silica”) and a synthetic amorphous silica produced by a precipitation method (hereinafter referred to as “silica gel”). "May be abbreviated as" precipitated silica "). The coating layer further contains other components as necessary.

The above-mentioned gelling method is well known. First, sodium silicate and sulfuric acid are instantaneously mixed and grown from a hydrosol to a hydrogel. After the grown hydrogel is washed with water, the surface area is controlled by heat treatment.
Thereafter, the hydrogel is dried and classified to produce a synthetic amorphous silica. The precipitation method is well known, and first, sodium silicate and sulfuric acid are mixed. The silica is precipitated in the solution by controlling the mixing conditions (temperature, silica concentration, time, etc.) at this time. The precipitated silica is precipitated and aged. This is a method for producing a synthetic amorphous silica by filtering aged silica, washing with water, drying, pulverizing, and classifying.

The specific surface area of the gelled silica is as follows:
Usually 300 to 500 m ² / g, 320 to 450 m ²
/ G is preferred. The specific surface area can be measured by a BET adsorption method. If the specific surface area is less than 300 m ² / g, the ink absorbency is poor and ink bleeding may occur. If the specific surface area exceeds 500 m ² / g, production of the ink jet recording paper may be difficult. On the other hand, when the specific surface area is within the preferred range, there is no such disadvantage, and
It is advantageous in that it has excellent ink absorbability and effectively prevents ink bleeding. The pore volume of the gelling silica is usually 1.0 ml / g or more, preferably 1.3 ml / g or more. If the pore volume is less than 0.5 ml / g, the ink absorbency may not be sufficient.

The average particle size of the gelled silica is as follows:
2.0-10.0 μm is preferred, and 3.0-10.0 μm
m is more preferred. Further, as the average particle size of the gelling silica, the lower limit of any of the numerical value range of the average particle size or any of the numerical values of the average particle size of the gelating silica employed in Examples described below. It is also preferable that the upper limit of any of the numerical ranges of the average particle diameter or the numerical range of which the upper limit is any of the numerical values of the average particle diameter of the gelling silica employed in Examples described later is used. The average particle size can be measured using a Coulter counter or the like. If the average particle size of the gelling silica is less than 2.0 μm, the coating suitability becomes insufficient due to the increase in viscosity, making the production difficult. If it exceeds 10.0 μm, the smoothness of the surface is increased. And the spread of dots may be large.

[0014] As the specific surface area of the precipitated silica is usually 250~500m ² / g, 300~400m ² /
g is preferred. The specific surface area can be measured by a BET adsorption method. When the specific surface area is less than 250 m ² / g, the ink absorbency is poor and ink bleeding may occur. When the specific surface area exceeds 500 m ² / g, production of the ink jet recording paper may be difficult. On the other hand, the specific surface area is
When it is within the above preferred range, it is advantageous in that it does not have the drawbacks, is excellent in ink absorbency, and effectively prevents ink bleeding. The pore volume of the precipitated silica is usually 1.0 ml / g or more, preferably 1.3 ml / g or more. When the pore volume is less than 0.5 ml / g,
The ink absorbency may not be sufficient.

The average particle size of the precipitated silica is as follows:
It is preferably from 3.0 to 8.0 μm, and more preferably from 5.0 to 8.0 μm. Further, as the average particle size of the precipitated silica, the lower limit of any of the numerical value range of the average particle size or any of the numerical values of the average particle size of the precipitated silica employed in Examples described later, It is also preferable that the upper limit of any one of the numerical ranges of the average particle diameter or the numerical range whose upper limit is any one of the numerical values of the average particle diameter of the precipitated silica employed in Examples described later is used. The average particle size can be measured using a Coulter counter or the like. When the average particle size of the precipitated silica is less than 3.0 μm, the applicability becomes insufficient due to thickening, and production may be difficult,
If it exceeds 8.0 μm, the smoothness of the surface may be poor and the spread of dots may be large.

In the present invention, the difference between the average particle size of the gelling silica and the average particle size of the precipitated silica (hereinafter sometimes referred to as “particle size difference”) is at least 1.0.
μm (1.0 μm or more), and more preferably at least 1.5 μm (1.5 μm or more). Further, as the particle size difference, a numerical range in which any one of the numerical values of the particle size differences adopted in Examples described later is a lower limit is also preferable. If the particle size difference is less than 1.0 μm, the writing properties may be poor. On the other hand, when the particle size difference is within the preferable numerical range, such a case does not occur, and the larger the particle size difference is, the better the writing performance is.

When the total content of the gelling silica and the precipitation silica in the coating layer is 100 parts by weight, the content of the gelling silica in the coating layer is 10 to 10 parts by weight. 60 parts by weight are preferred, and 20 to 40 parts
More preferably, the content of the precipitated silica in the coating layer is 40 to 90 parts by weight, and more preferably 60 to 80 parts by weight. In addition, as the content of the gelling silica in the coating layer, the lower limit of any one of the preferred numerical range or the numerical value of the content of the gelling silica used in Examples described below is a lower limit. It is also preferable that the upper limit of any of the above preferable numerical ranges or the numerical range of which the upper limit is any of the numerical values of the content of the gelling silica employed in Examples described later is used. On the other hand, as the content of the precipitated silica in the coating layer, the lower limit of any one of the lower limit of the preferred numerical range or the numerical value of the content of the precipitated silica adopted in Examples described below, A numerical range having an upper limit of any of the above preferable numerical ranges or a numerical value of the content of precipitated silica employed in Examples described later is also preferable.

When the content of the gelling silica in the coating layer is less than 10 parts by weight, that is, when the content of the precipitation silica exceeds 90 parts by weight, the writability is poor. Undesirably, when the content of the gelling silica in the coating layer exceeds 60 parts by weight, that is, when the content of the precipitation method silica is less than 40 parts by weight, the spread of the ink dots is large. It is not preferable because it becomes too much.

In the present invention, the gelling silica and the precipitation silica may be appropriately prepared or commercially available.

The other components are not particularly limited and may be appropriately selected depending on the use and purpose of the ink jet recording paper. Examples thereof include a binder, a surfactant, a cationic polymer, a pigment, and a lightfastness improver. , Additives and the like. Among these, the coating layer is a binder,
An embodiment containing at least one of a surfactant and a cationic polymer is preferred.

Examples of the binder include a water-soluble binder and a water-dispersible binder. Examples of the water-soluble binder include starch, cationized starch, casein, gelatin, carboxymethylcellulose, hydroxyethylcellulose, polyvinylpyrrolidone, and the like. Examples of the water-dispersible polymer include styrene butadiene latex and acrylic emulsion. These may be used alone or in combination of two or more.

Examples of the surfactant include anionic surfactants such as carboxylate, sulfonate, sulfate and phosphate, ether-type and ether-ester nonionic surfactants, and betaine. And amphoteric surfactants such as aminocarboxylic acid salts and imidazoline derivatives. Among these surfactants, sulfonates are preferred, and dialkyl sulfonates such as sodium dimethylpentyl sulfonate are particularly preferred. When a dialkyl sulfonate is used as the surfactant, the content thereof is usually 1 to 10 parts by weight, based on 100 parts by weight of the total of gelling silica and precipitation silica in the coating layer. , 1 to 5 parts by weight. If the content is less than 1 part by weight, the ink absorbency tends to be insufficient, and if it exceeds 10 parts by weight, the color density tends to decrease.

Examples of the cationic polymer include cationic polyacrylamide, cationic polystyrene copolymer, polydimethyldiallylammonium chloride, polyamine polyamide epichlorohydrin (polyamide polyamine epichlorohydrin), polyethyleneimine, polyamine sulfone and colloidal silica. Resins. These may be used alone or in combination of two or more. Among these cationic polymers, cationic polyacrylamide and polyamine polyamide epichlorohydrin are preferable in terms of water resistance.

The above-mentioned cationic polyacrylamide is a copolymer of acrylamide and a cationic monomer. In some cases, it may be a terpolymer obtained by further adding (meth) acrylic acid as a monomer component and copolymerizing. As the cationic monomer, for example,
General formula CH ₂ ＣC (R ₁ ) COOC _n H _2n N (R ₂ ) (R ₃ )
A compound of the general formula CH ₂ ＣC (R ₁ ) CONHC
_n H _2n N (R ₂₎ such as compounds represented by (R ₃₎ can be mentioned. In these general formulas, R ₁ represents a hydrogen atom or a lower alkyl group. R ₂ and R ₃ represent a lower alkyl group. n represents an integer of 1 to 5. Specific examples of the cationic monomer include dimethylaminoethyl methacrylate [CH ₂ ＣC (CH ₃ ) COOCH ₂ CH ₂ N (CH ₃ )
₂ ], diethylaminoethyl methacrylate [CH ₂ ＣC
(CH ₃ ) COOCH ₂ CH ₂ N (CH ₂ CH ₃ ) ₂ ], dimethylaminoethyl methacrylate chloride salt [CH ₂
ＣC (CH ₃ ) COOCH ₂ CH ₂ N (CH ₃ ) ₂ ] · C
l, dimethylaminopropylacrylamide [CH ₂ =
CHCONHCH ₂ CH ₂ CH ₂ N (CH ₃ ) ₂ ] and the like.

The cation value of the cationic polyacrylamide can be measured, for example, as follows. That is, about 0.1 g of a sample was precisely weighed and diluted with a diluent (water / methanol / acetic acid = 89/10/1% by volume).
/ 400 titration with aqueous polyvinyl potassium sulfate (PVSK) solution, the following formula: (titration (ml) × 1/400 × factor (PVSK)) / (sample collection amount (g) × nonvolatile content (%) / 100) , Can be calculated.
The cationization of the cationic polyacrylamide is preferably, for example, 1.5 to 5.0 (meq / gNV). The molecular weight of the cationic polyacrylamide is preferably, for example, 500,000 to 1.2 million.

As the cationic polystyrene copolymer, for example, a compound having the structure shown in Chemical formula 1 can be mentioned.

[0027]

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In this structural formula, l, m and n each represent a numerical value of 1 or more, preferably l and m are numerical values of 10 or more, and n is a numerical value of 1 or more. The cation value of the cationic polystyrene copolymer can be measured in the same manner as in the case of the cationic polyacrylamide, for example,
1.5 to 5 (meq / gNV) is preferred. As the molecular weight of the cationic polystyrene copolymer, for example,
5,000,000 is preferred.

As the polydimethyldiallylammonium chloride, for example, a compound having a structure represented by Chemical Formula 2, a compound having a structure represented by Chemical Formula 3, and the like are preferably exemplified.

[0030]

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[0031]

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In these structural formulas, n represents the degree of polymerization. The cation value of the polydimethyldiallylammonium chloride can be measured in the same manner as in the case of the cationic polyacrylamide, and is, for example, 1.5 to 5.0 (meq).
/ GNV) is preferred. The molecular weight of the polydimethyldiallylammonium chloride is, for example, 10,000 to
100,000 is preferred.

The polyamine polyamide epichlorohydrin is also called an epixylated polyamide resin and is a compound represented by the following structural formula.

[0034]

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The above-mentioned polyamine polyamide epichlorohydrin is obtained by mixing a diamine containing a secondary amine in the molecule (eg, diethylenetriamine) with a dicarboxylic acid (eg,
It is obtained by adding epichlorohydrin to a secondary amino group in a polyamide polyamine obtained by a dehydration-condensation reaction with adipic acid) and, after completion of the reaction, adjusting the pH to an acidic side with hydrochloric acid. The cation value of the polyamine polyamide epichlorohydrin can be measured in the same manner as in the case of the cationic polyacrylamide, and is preferably, for example, 1.5 to 5.0 (meq / gNV).
The molecular weight of the polyamine polyamide epichlorohydrin is preferably, for example, 20,000 to 150,000.

The content of the cationic polymer in the coating layer is preferably from 20 to 70 parts by weight based on 100 parts by weight of the total of the gelling silica and the precipitation silica.

Examples of the pigment include, in addition to the above-mentioned gelled silica and precipitated silica, calcium carbonate, kaolin, talc, clay, diatomaceous earth, magnesium silicate, calcium silicate, alumina, zeolite, barium sulfate, urea resin, melamine White pigments such as resin are exemplified.

Examples of the light resistance improver include zinc sulfate, zinc oxide, hindered amine antioxidants, and benzotriazole ultraviolet absorbers such as benzophenone. In the present invention, among these, zinc sulfate is preferred.

Examples of the additives include pigment dispersants, thickeners, defoamers, dyes, fluorescent brighteners, preservatives, pH
And an adjusting agent.

The coating layer in the present invention is obtained by applying a coating liquid containing the above-mentioned gelling silica, the above-mentioned precipitation silica and, if necessary, other components onto the above-mentioned base paper and drying it. Formed by The coating layer thus formed functions as an ink receiving layer in the ink jet recording paper.

The means for applying the coating liquid on the base paper is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a curtain coater, a roll coater, a reverse roll coater, and an air knife coater. , A blade coater, a spray coater, a spin coater and the like. In the present invention, among these, a curtain coater is preferable in that the coating surface of the coating liquid, that is, the surface of the coating layer can have excellent smoothness.

The coating amount of the coating liquid applied on the base paper is usually 6 to 10 g / m ² in solid content,
8 to 10 g / m ² is preferred. If the coating amount is less than 6 g / m ² in solid content, the ink absorbency may be insufficient, and if it exceeds 10 g / m ² , the color density may be reduced due to white dropout. On the other hand, the coating amount is
When it is within the above preferred range, it is advantageous in that it does not have the above-mentioned drawbacks, is excellent in ink absorbency, has a small spread of ink dots, and can be produced with good writing properties.

In the present invention, the coating layer may have a single-layer structure or a laminated structure according to the use and purpose of the ink jet recording paper. The coating layer having a laminated structure is formed by applying the coating liquid on a base paper and then applying the coating liquid on the application surface.
The smoothness of the coating layer in the inkjet recording paper of the present invention is preferably 15 to 80 seconds in Beck's smoothness, and more preferably 20 to 65 seconds. When the Beck smoothness is less than 15 seconds, there is a feeling of flat surface roughness,
If the time exceeds seconds, the writing property may be poor. The Beck smoothness can be measured using, for example, a commercially available Beck smoothness meter.

In the ink jet recording paper of the present invention, a back coat layer may be formed on the surface of the base paper opposite to the side on which the coating layer is formed. When the back coat layer is formed on the ink jet recording paper, it is advantageous in that curling, shrinkage and the like of the ink jet recording paper can be effectively prevented. The back coat layer is formed, for example, by applying a liquid for forming a back coat layer on the surface of the base paper opposite to the side on which the coating layer is formed.

The liquid for forming the back coat layer contains an anionic surfactant and, if necessary, further contains an antifoaming agent, a foam inhibitor, a dye, a fluorescent whitening agent, a preservative and the like. You may.

Examples of the anionic surfactant include (A) a carboxylic acid type, (B) a tester sulfate type,
Surfactants such as (C) sulfonic acid type and (D) other hydrophilic groups. Examples of the carboxylic acid (A) include fatty acids, rosin acid soaps, and ether salts. As the (B) sulfate ester type,
Examples thereof include alkyl sulfates, sulfates of sulfated oils and fatty acid esters, sulfates of fatty acid amides, and glycol ether sulfates. Examples of the sulfonic acid (C) include alkyl sulfonates, dialkyl sulfosuccinates, alkyl allyl sulfonates, alkyl naphthalene sulfonates, alkyl amide sulfonates, and alkyl ester sulfonates. As the other hydrophilic group (D), for example,
Phosphate esters and the like. In the present invention, among these, dialkyl sulfosuccinates are preferred, and diethylhexyl sulfosuccinate is more preferred. As the sulfosuccinic acid diethylhexyl ester salt, in particular, sulfosuccinic acid di2
Ethylhexyl ester is preferred. When di-sulfosuccinic acid diethylhexyl ester is used as the anionic surfactant, its content in the liquid for forming a back coat layer is preferably 0.001 to 0.03% by weight.

The liquid for forming the back coat layer has a surface tension of usually 25 to 40 dyn / cm. The application amount of the liquid for forming the back coat layer is preferably 5 cc / m ² or more. Means for applying the liquid for forming the back coat layer include, for example, a curtain coater, a bar coater, a gravure coater, a roll coater, a reverse roll coater, an air knife coater, a blade coater, a spray coater, a spin coater and the like.

When the coating layer has a laminated structure,
Each time a coating layer is formed, it is preferable to apply the liquid for forming a back coat layer to the opposite surface.

When the ink jet recording paper of the present invention is manufactured, the coating liquid is applied on one surface of a base paper,
After applying the back coat layer forming liquid to the other surface of the base paper, it is preferable to dry these coated surfaces. The drying temperature is preferably 80 ° C. or higher, and more preferably 100 ° C. or higher, from the viewpoint that curl adjustment can be performed efficiently. As the drying method, a method using a drum dryer is preferable, and a method is preferable in which the coating surface of the liquid for forming the back coat layer is brought into contact with the drum dryer, and drying is performed.

On the inkjet recording paper of the present invention, for example, a recorded image can be formed by using a general-purpose inkjet printer, but it is also possible to form a recorded image by using a high-resolution inkjet printer.

Examples of the recording liquid applied to the ink jet recording paper of the present invention include a dye-type recording liquid and a pigment-type recording liquid. Examples of the dye-type recording liquid include a recording liquid containing a water-soluble dye such as a direct dye, an acid dye, a reactive dye, and a basic dye. As the dye-type recording liquid, recording liquids of four colors, yellow, magenta, cyan and black, are usually used. In the recording liquids of the respective colors, one or two or more water-soluble dyes are used in all ink compositions. 0.2 to 15 parts by weight, preferably 0.5 to 10 parts by weight,
More preferably, 2 to 9 parts by weight are added.

The recording liquid can be used by mixing a solvent in addition to water. Examples of the solvent include: methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, pentyl alcohol,
C1-C10 alkyl alcohols such as hexyl alcohol, heptyl alcohol, octyl alcohol, nonyl alcohol, and decyl alcohol; for example, cyclopentane, hexane, cyclohexane, heptane, octane, nonane, decane, undecane, dodecane, tridecanone, Aliphatic or aromatic hydrocarbon solvents represented by tetralin, decalin, benzene, toluene, xylene and the like; for example, carbon tetrachloride, trichloroethylene,
Halogenated hydrocarbon solvents such as tetrachloroethylene, dichlorobenzene, etc .; ether solvents such as ethyl ether, butyl ether, ethylene glycol diethyl ether, ethylene glycol monoethyl ether, etc .; eg, acetone, methyl ethyl ketone, methyl propyl ketone, Ketone solvents such as methyl amyl ketone and cyclohexanone; ester solvents such as ethyl formate, methyl acetate, ethyl acetate, propyl acetate, butyl acetate, phenyl acetate, ethylene glycol monoethyl ether acetate, and ethyl lactate; Polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, and glycerin; other amines, amides, N-methyl- -Nitrogen-containing heterocyclic systems such as -pyrrolidone and 1,3-dimethyl-2-imidazolidinone, and intramolecular ester solvents of oxycarboxylic acids such as valerolactone and caprolactone, dimethyl sulfone, diethyl sulfone, and bis (2-chloroethyl) Sulfone, aliphatic sulfone compound-based solvent such as methylsulfonylacetonitrile,
Various solvents such as alicyclic sulfone compound solvents such as sulfolane and sulfolene, and sulfoxide compound solvents such as tetramethylene sulfoxide and 3-methyltetramethylene sulfoxide.

The pigment type recording liquid is preferably a recording liquid in which pigment fine particles are dispersed in an aqueous dispersion medium containing a polymer having a hydrophilic component and a hydrophobic component and a water-soluble organic solvent. . Examples of the polymer include polyacrylic acid having a molecular weight of about 1,000 to 100,000,
Examples include polymethacrylic acid, condensed naphthalenesulfonic acid, styrene-maleic acid, and the like. These polymers can be dissolved or dispersed in an aqueous liquid by forming a salt. Examples of the components that form the polymer salt include alkali metals, aliphatic amines,
Alcohol amine, morpholine, N-morpholine and the like. Examples of the water-soluble organic solvent include, for example, alcohols. In the present invention, polyhydric alcohols are particularly preferable.

By mixing and dispersing the pigment fine particles together with the polymer, the aqueous organic solvent, and water, a recording liquid having a predetermined viscosity range can be obtained. Examples of the pigment fine particles used in the recording liquid include, for example, an azo type, a phthalocyanine type,
Quinacridone, anthraquinone, dioxazine,
Various known organic pigments such as indigo and perinone are exemplified.

[0055]

EXAMPLES Examples of the present invention will be described below, but the present invention is not limited to these examples.

(Example 1) <Preparation of base paper> 80 parts by weight of LBKP and 2 parts by weight of NBKP
The wood pulp consisting of 0 parts was beaten using a disc finale to obtain a pulp slurry having a Canadian freeness of 400 ml. While stirring the obtained pulp slurry, 5 parts by weight of talc, 1.2 parts by weight of rosin, 1.5 parts by weight of starch, and 1.5 parts by weight of aluminum sulfate were added to 100 parts by weight of the pulp. Base paper having a basis weight of 80 g / m ^{2 was made} by a paper machine. Oxidized starch was converted to a solid content of 1.0 g /
m ^{2 was} adhered to obtain a base paper for coating. Base paper thickness is 95μ
m, Cobb water absorption was 21.0 g / m ² .

<Preparation of Coating Liquid and Formation of Coating Layer> Gelated silica 35 parts by weight (specific surface area: 360 m ² / g, average particle size: 8.0 μm) Precipitation method silica: 65 parts by weight (specific surface area: 360 m) ² / g, average particle size 6.0 μm) Silanol-modified polyvinyl alcohol 45 parts by weight Polyamine polyamide epichlorohydrin 35 parts by weight Sodium dimethylpentylsulfonate 2 parts by weight Water was added to the above composition to obtain a solid content of 20% by weight. A coating liquid was used. This coating solution was applied to the above-mentioned base paper as a solid content of 8 g / m ² by a curtain coater and subjected to on-machine gloss calendering to produce inkjet recording paper. The average particle size is a value measured using a commercially available Coulter counter.

(Examples 2 to 3 and Comparative Examples 1 to 6) In Example 1, the average particle size (μm) and the content (parts by weight) of the gelling silica and the precipitated silica in the coating solution were shown. An ink jet recording paper was manufactured in the same manner as in Example 1 except that the value was set to 1.

With respect to the manufactured ink jet recording paper, the spread of ink dots, writability and smoothness were evaluated. The results are shown in Table 1. <Evaluation> (1) Spreading of Ink Dots Aqueous ink (black) was applied to a printer (Canon: BJ
C-400J) standard mode printing, and then the printing is performed using an image analyzer (manufactured by Nippon Avionics: SPI).
CA II) was used to measure the extent of the spread of the ink dots. The evaluation criteria were the following three levels. In addition, ○
If so, there is no practical problem. ○ = Ink dot diameter of less than 0.2 mm △ = Ink dot diameter of 0.2 mm or more and less than 0.3 mm × = Ink dot diameter of 0.3 mm or more (2) Writability For ink jet recording paper The writing quality when handwritten with a pencil having a hardness of H was evaluated according to the following criteria. ◎: Very easy to write ○: Easy to write △: Slightly difficult to write, but acceptable for practical use ×: Hard to write, poor writability, causing practical problems Certain conditions (3) Smoothness Smoothness of the surface of the obtained inkjet recording paper (seconds)
Was measured using a Beck smoothness meter (manufactured by Kumagai Riki Co., Ltd .: Beck smoothness meter).

[0060]

[Table 1]

From the results in Table 1, the following is clear. That is, when only the gelling silica is used (Comparative Example 1), the spread of the dots becomes too large. When only the precipitated silica is used (Comparative Example 2), the writability is insufficient. Even when gelling silica and precipitation silica are used in combination, if the content of both is out of the range described in claim 1 (Comparative Examples 3 and 4), gelling silica is too small ( Comparative Example 3) Writability is insufficient, and if the amount of gelling silica is too large (Comparative Example 4), the spread of dots becomes large. If the average particle size of the precipitated silica exceeds 8 μm (Comparative Example 5), the spread of the dots is slightly increased even when both the gelling silica and the precipitated silica are used.
On the other hand, when both gelling silica and precipitation silica are used and the content of both is within the range described in claim 1 (Examples 1 to 4), the spread of the dots is small, and the The properties are good, and the smoothness is also in a preferable range. In addition,
When the difference in the average particle size between the gelling silica and the precipitation silica is less than 1 (Example 4), the writability is slightly inferior.
When the above is excellent, the writability is excellent (Examples 1 to 3). In particular, when the difference in the average particle diameter is 5 and the largest (Example 3)
Extremely excellent in writability.

[0062]

According to the present invention, the above-mentioned conventional problems can be solved. Further, according to the present invention, it is possible to provide an ink jet recording sheet having a high ink absorbency, a small spread of dots, and a good writability.

Claims (3)

[Claims] 1. In an ink jet recording paper having a coating layer provided on a base paper, the coating layer is formed by 10 to 60 parts by weight of synthetic amorphous silica produced by a gelling method and by a precipitation method. An ink jet recording sheet containing 40 to 90 parts by weight of synthetic amorphous silica. 2. The synthetic amorphous silica produced by the gelation method has an average particle size of 2.0 to 10.0 μm, and the synthetic amorphous silica produced by the precipitation method has an average particle size of 3. 0-8.0
μm, and the difference between the average particle diameter of the synthetic amorphous silica produced by the gelling method and the average particle diameter of the synthetic amorphous silica produced by the precipitation method is at least 1.0 μm. Item 2. An ink jet recording sheet according to item 1. 3. The ink jet recording sheet according to claim 1, wherein the coating layer has a Beck smoothness of 15 to 80 seconds.