JP2003305948A - Image receiving coating agent for ink jet recording and ink jet recording sheet - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink jet recording sheet having both of ink drying properties and the water resistance of a recording image, and an image receiving coating agent for ink jet recording capable of manufacturing the recording sheet. <P>SOLUTION: The image receiving coating agent for ink jet recording contains a (meth)acrylamide copolymer emulsion (A), which is obtained by the emulsion polymerization of a monomer mixture comprising 5-80 wt.% of (a1) a hydrophilic ethylenic unsaturated monomer containing (meth)acrylamide and 20-95 wt.% of (a2) a hydrophilic ethylenic monomer in an aqueous medium in the presence of a chain transfer agent (b) comprising phosphorous acid or a salt thereof using a surfactant (c) and a polymerization initiator (d), a cationic compound (B) and an inorganic filler (C). The ink jet recording sheet is obtained by providing the image receiving layer formed by using the image receiving coating agent on a sheet support. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ink jet image-receiving coating agent, and an ink jet recording sheet produced using the same.

[0002]

2. Description of the Related Art In recent years, various types of printers for computer output have become popular. Among them, the inkjet recording method has been attracting attention because it can easily achieve high-speed recording, colorization, and high density, and it has excellent quietness, cost, and image quality. Since it has excellent performance not found in the market, it is expected to further spread. By the way, in ink jet recording, in order to prevent nozzle clogging, an ink in which a water-soluble dye or the like is dissolved in an aqueous solvent and which dries slowly is used. Therefore, even if the recording paper is water-absorbent such as paper, it is necessary to further accelerate the drying. Further, in the case of a non-water-absorbing material such as a plastic film, the drying property of the ink after printing is further poor. Therefore, an ink-absorbing image receiving layer is usually provided on the plastic film which is a support.

However, even a constitution in which an image receiving layer is provided on a support such as a plastic film has not been obtained with sufficient performance. For example, a method has been proposed in which the image-receiving layer is composed of a water-soluble resin, a hydrophilic resin, or the like in order to improve the wettability, dyeability, or absorbability of the slow-drying ink. However, both of them are absorbed by the aqueous solvent or in a high-humidity environment, the image-receiving layer becomes wet and becomes sticky, blocking the recording medium when stacked, or poorly dried and easily soiled by touching after printing. And so on. That is, the properties of wettability, dyeing property and absorbability, and the properties of water resistance, drying property and blocking resistance are contradictory properties, and a property satisfying them at the same time has not been obtained.

[0004]

The problems of the conventional image-receiving layer are summarized below. 1. When the image receiving layer is water-soluble, the water resistance of the recorded image is insufficient. 2. The ink absorbency is poor, and when a large amount of ink is applied, the drying and fixing of the ink is slow. 3. When trying to obtain a color image, the inks of multiple colors are stacked one after another before being fixed on the paper,
A sharp character or recorded image cannot be obtained because the area around the dot is jagged or the area around the character or image is blurred. 4. The color developability of the ink on the surface of the image receiving layer becomes insufficient, and the color reproducibility tends to be poor.

In order to solve these problems, for example, as means for increasing the water resistance of recorded images, Japanese Patent Laid-Open No. 56-9969 has been proposed.
Japanese Patent Publication No. 3 discloses an inkjet recording paper containing a halogenated quaternary ammonium salt or the like. Further, JP-A-60-220750 discloses a recording sheet in which a hydrophilic film made of water-soluble polyvinyl alcohol having a saponification degree of 70 to 90 mol% is provided on a polyester film. Furthermore, JP-A-1-190483
The publication discloses an inkjet recording sheet in which the water resistance of a recorded image is improved by providing an ink absorbing layer containing a water-soluble polymer and a cationic crosslinking agent. However, there has not been obtained a material that achieves both the drying property of the ink and the water resistance of the recorded image.

Therefore, an object of the present invention is to provide an inkjet recording sheet having the following characteristics, and an inkjet image-receiving coating agent capable of producing the recording sheet. (1) It has good ink fixability and good quality of a recorded image. (2) Sufficient image density is obtained and the solid image is highly uniform. (3) No bleeding of recorded images occurs. (4) Color reproducibility is good and high-definition images can be obtained. (5) The recorded image has water resistance.

[0007]

The ink jet image-receiving coating agent of the present invention comprises a shell made of a hydrophilic polymer and a core made of a hydrophobic polymer, which are emulsion-polymerized by a specific method to perform a protective colloid function. A (meth) acrylamide-based copolymer emulsion in a form in which
Since it contains a cationic compound and an inorganic filler, the ink jet recording sheet produced by using this has both excellent ink acceptability and water resistance of a recorded image.

That is, the present invention provides a hydrophilic ethylenically unsaturated monomer (a1) containing 5 to 80% by weight of (meth) acrylamide and / or a derivative thereof, and a hydrophobic ethylenically unsaturated monomer (a2) 20. ˜95% by weight of a monomer mixture in an aqueous medium in the presence of a chain transfer agent (b) consisting of hypophosphorous acid or a salt thereof, using a surfactant (c) and a polymerization initiator (d). An ink jet image-receiving coating agent comprising a (meth) acrylamide-based copolymer emulsion (A) obtained by emulsion polymerization, a cationic compound (B), and an inorganic filler (C). . Further, the present invention is an inkjet recording sheet having an image receiving layer formed by using the inkjet image receiving coating agent on a sheet base material.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION First, the ink jet image-receiving coating agent of the present invention will be described. The (meth) acrylamide-based copolymer emulsion (A) contained in the image-receiving coating agent is a film-forming component and is a hydrophilic ethylenically unsaturated monomer (a1) containing (meth) acrylamide and / or its derivative. ) 5-80% by weight, and hydrophobic ethylenically unsaturated monomer (a2) 20-95
Emulsification of a monomer mixture consisting of wt.% In an aqueous medium in the presence of a chain transfer agent (b) consisting of hypophosphorous acid or a salt thereof, using a surfactant (c) and a polymerization initiator (d). It is polymerized.

The (meth) acrylamide copolymer emulsion (A) emulsifies a monomer mixture consisting of a hydrophilic ethylenically unsaturated monomer (a1) and a hydrophobic ethylenically unsaturated monomer (a2) by a specific method. Since it is formed by polymerization, it has a form in which a shell made of a hydrophilic polymer that sequentially generates during the polymerization and performs a function like a protective colloid is bonded to a core made of a hydrophobic polymer. Therefore, the film of the (meth) acrylamide-based copolymer emulsion (A) has excellent water resistance.

The hydrophilic ethylenically unsaturated monomer (hereinafter, also referred to as hydrophilic monomer) (a1) is (meth)
By containing acrylamide and / or its derivative as an essential component, it becomes a hydrophilic polymer that constitutes a shell that functions as a protective colloid by polymerization. As a derivative of (meth) acrylamide, N-methylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-ethoxymethyl (meth) acrylamide,
N- (n-, iso) butoxymethyl (meth) acrylamide, N-methoxyethyl (meth) acrylamide, N
-Ethoxyethyl (meth) acrylamide, N- (n
N-alkoxyalkyl (meth) acrylamides such as-, iso) butoxyethyl (meth) acrylamide, and 2- (meth) acrylamide-2-methylpropanesulfonic acid, N, N-dimethyl (meth) acrylamide,
Examples thereof include N, N-diethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N-isopropylacrylamide, N-vinylpyrrolidone, diacetone (meth) acrylamide, N-vinylacetamide. The (meth) acrylamide and its derivative can be used alone or in admixture of two or more. In particular, from the viewpoint of Newtonian fluidity of the obtained copolymer emulsion (A), the hydrophilic monomer (a1) is acrylamide and / or N-.
It is preferred to include methylol acrylamide.

The hydrophilic monomer (a1) other than (meth) acrylamide and its derivative has a hydrophilic functional group such as carboxyl group, hydroxyl group, phosphoric acid group, sulfonic acid group,
It is an ethylenically unsaturated monomer having an amino group, an epoxy group and the like. Specific examples of the monomer having a carboxyl group include (meth) acrylic acid, (anhydrous) maleic acid,
Maleic acid monoalkyl ester, fumaric acid, fumaric acid monoalkyl ester, crotonic acid, itaconic acid, itaconic acid monoalkyl ester, itaconic acid glycol monoether, citraconic acid, citraconic acid monoalkyl ester, cinnamic acid, and the like, and alkalis thereof. Metal salt,
Examples thereof include amine salts and ammonium salts. Specific examples of the monomer having a hydroxyl group include (meth) allyl alcohol, hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, and triethylene glycol mono (meth) acrylate.

Specific examples of the monomer having a phosphoric acid group include 2-hydroxyethyl (meth) acryloyl phosphate, phenyl-2-acryloyloxyethyl phosphate, 2-acryloyloxyethylphosphonic acid and salts thereof. Specific examples of the monomer having a sulfonic acid group include vinyl sulfonic acid, allyl sulfonic acid, styrene sulfonic acid, sulfopropyl (meth)
Examples thereof include acrylate, 2-hydroxy-3- (meth) acryloxypropyl sulfonic acid and salts thereof. Specific examples of the monomer having an amino group include aminoethyl (meth) acrylate, N-methylaminoethyl (meth) acrylate, N-ethylaminoethyl (meth) acrylate, N, N-dimethylaminoethyl (meth) acrylate, N, N-diethylaminoethyl (meth) acrylate etc. are mentioned. Specific examples of the monomer having an epoxy group include glycidyl (meth) acrylate. Other examples include N-vinylpyrrolidone and N-vinyloxazoline monomers.

The content of (meth) acrylamide and / or its derivative based on the total amount of the hydrophilic monomer (a1) is preferably 30 to 100% by weight, and 50 to 10% by weight.
0% by weight is more preferred. When the content of (meth) acrylamide and / or its derivative is less than 30% by weight, the drying property of the obtained copolymer emulsion (A) and the water resistance of the film when formed are insufficient. . The content of the hydrophilic monomer (a1) based on the total amount of the monomer mixture is 5 to 80% by weight, preferably 15 to 70% by weight, and more preferably 25 to 60% by weight. Content of hydrophilic monomer (a1) is 5% by weight
If it is less than the above range, the stability and rheological properties of the obtained copolymer emulsion (A) are deteriorated. On the other hand, when it exceeds 80% by weight, the water resistance of the film formed by using the obtained copolymer emulsion (A) is lowered, or the solid content of the obtained emulsion is lowered due to the increase of viscosity, and When it is used as an image-receiving coating agent, it causes poor drying and poor strength.

The hydrophobic ethylenically unsaturated monomer (hereinafter, also referred to as hydrophobic monomer) (a2) becomes a hydrophobic polymer constituting the core by polymerization. Specific examples of the hydrophobic monomer include styrene, α-methylstyrene,
Methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, iso-butyl (meth) acrylate, tert-butyl (meth) acrylate, benzyl (meth) acrylate, cyclohexyl (meth) acrylate, 2- Examples thereof include ethylhexyl (meth) acrylate, octyl (meth) acrylate, isododecyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, vinyl acetate and ethylene.

The content of the hydrophobic monomer (a2) based on the total amount of the monomer mixture is 20 to 95% by weight,
Preferably 30 to 85% by weight, more preferably 40 to
It is 75% by weight. The hydrophilic monomer (a1) and the hydrophobic monomer (a2) are selected in consideration of required hardness of the image receiving layer and hydrophilicity.

Water can be used as the aqueous medium. Further, in order to impart coating suitability to the image-receiving coating agent and to improve the drying property, a water-miscible organic solvent may be used in combination within the range of 30% by weight or less of the aqueous medium. Examples of the water-miscible organic solvent include alcohol solvents (for example, methanol, ethanol, isopropanol, ethylene glycol, glycerin, etc.), ketone solvents (for example, acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.), ether solvents (for example, ethylene. Glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, propylene glycol monomethyl ether, tetrahydrofuran, etc.), amide solvents (eg, dimethylformamide, dimethylacetamide, etc.), sulfoxide solvents (eg, dimethyl sulfoxide, etc.) To be These water-miscible organic solvents can be used alone or in admixture of two or more.

The chain transfer agent (b) composed of hypophosphorous acid or a salt thereof is used together with the surfactant (c) in radical polymerization of a monomer mixture, whereby the molecular weight and molecular weight distribution of the resulting copolymer can be controlled. Acts to regulate. Compared with other chain transfer agents, hypophosphorous acid or a salt thereof has a smaller dissociation energy of the intramolecular PH bond, so that hydrogen is easily extracted, the molecular weight is easily controlled, and there are few aggregates and a low viscosity. Copolymer emulsions can be produced. Examples of the salt of hypophosphorous acid include sodium salt, potassium salt, ammonium salt, amine salt and the like, and even a hydrate can be used.

Further, when radically polymerizing the monomer mixture, unless the water solubility is lowered, it is within the range of 50% by weight or less based on the total amount of the chain transfer agent and 3% by weight or less based on the total amount of the monomers. Within the range, other chain transfer agents can be used in combination. The other chain transfer agent is not particularly limited as long as it is soluble in water or a monomer, and for example, thiols, thiol acids, secondary alcohols, amines and the like can be used. Specific examples of other chain transfer agents include thiol benzoate, mercaptoethanol, mercaptopropanol, thioglycolic acid, thiomalic acid, triethyleneglycol dimercaptan, and isopropanol.

The amount of the chain transfer agent (b) used consisting of hypophosphorous acid or its salt varies depending on the composition of the monomer and the kind and amount of the organic solvent in the aqueous medium, but is 0.001 based on the total amount of the monomer. It is preferably in the range of 10 to 10% by weight, and more preferably in the range of 0.01 to 5% by weight. When the amount of the chain transfer agent (b) used exceeds 10% by weight, the water-soluble component may increase, which is not preferable. Further, when it is less than 0.001% by weight, the molecular weight of the obtained copolymer becomes high, the viscosity of the image-receiving coating agent becomes high, or the solid content after the viscosity adjustment becomes small,
This adversely affects the coatability of the image-receiving coating agent and the performance of the image-receiving layer.

Examples of the surfactant (c) include anionic surfactants, cationic surfactants, nonionic surfactants and amphoteric surfactants, which may be used alone or in admixture of two or more. Can be used. These surfactants may have an ethylenically unsaturated double bond.
Examples of the anionic surfactant include lauryl sulfate, polyoxyethylene alkyl ether sulfate, alkylbenzene sulfonate, polyoxyethylene alkyl ether sulfate, polyoxyethylene alkylphenyl ether sulfate, N-acyl amino acid salt, alkyl phosphorus. Acid salt,
Examples thereof include alkane sulfonate, oleate, stearate, alkylnaphthalene sulfonate, dialkyl sulfosuccinate, alkyl diphenyl ether disulfonate, and naphthalene sulfonic acid formalin condensate salt. Examples of the cationic surfactant include benzalkonium chloride, benzethonium chloride, stearyltrimethylammonium chloride, distearyldimethylammonium chloride, and lauryltrimethylammonium chloride.

Examples of nonionic surfactants include polyol fatty acid ester, glyceryl monostearate, oleophilic glyceryl monooleate, ethylene glycol monostearate, propylene glycol monostearate, sorbitan fatty acid ester, and polyoxyethylene sorbitan fatty acid ester. , Polyoxyethylene fatty acid ester, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene sorbitol fatty acid ester, N-acyl amino acid ester, sucrose fatty acid ester, fatty acid alkylolamide and the like.

As the amphoteric surfactant, an amino acid type amphoteric surfactant such as alkyldiaminoethylglycine hydrochloride,
Examples thereof include betaine-type amphoteric surfactants such as 2-alkyl-N-carboxymethyl-N-hydroxyethylimidazolinium betaine and lauryldimethylaminoacetic acid betaine. The amount of the surfactant (c) used is preferably 0.01 to 20% by weight, based on the total amount of the monomers, and is preferably 0.
1 to 15% by weight is more preferable. When the amount of the surfactant (c) used is less than 0.01% by weight, aggregates are likely to be formed during emulsion polymerization, and stability during polymerization is poor. Also, 2
Copolymer emulsion (A) obtained when it exceeds 0% by weight
The water resistance of the film formed by using is decreased and the cost is increased.

The polymerization initiator (d) is a compound that generates radicals in the polymerization temperature range to induce the polymerization reaction. As the polymerization initiator (d), organic or inorganic peroxide-based polymerization initiators, redox-based polymerization initiators, or azo-based polymerization initiators can be used alone or in combination of two or more. Examples of redox-based polymerization initiators include peroxides such as hydrogen peroxide, persulfates (sodium persulfate, potassium persulfate, ammonium persulfate, etc.), hydroperoxides, ferric chloride, ferric sulfate, and the like. Examples include combinations with reducing agents such as sodium bisulfite, ascorbic acid, polyamines and the like.

When acrylamide is used as the hydrophilic monomer (a1) in synthesizing the (meth) acrylamide copolymer emulsion (A), a peroxide initiator can be used. However, when an acrylamide derivative having a crosslinkable functional group such as N-methylol group or N-alkoxymethyl group is used, the use of a peroxide-based polymerization initiator induces crosslinking of the crosslinkable functional group during emulsion polymerization. However, gelation occurs and the stability of the resulting copolymer emulsion (A) is impaired. On the other hand, an azo-based polymerization initiator is different from a peroxide-based polymerization initiator or a redox-based polymerization initiator in that it has a small hydrogen abstraction action, and an acrylamide derivative having a crosslinkable functional group using the azo-based polymerization initiator. In the case of emulsion-polymerizing a monomer mixture containing N, the N-methylol group and the N-alkoxyalkyl group are unlikely to self-condense during the polymerization reaction. Therefore, the azo polymerization initiator is preferably used.

The azo polymerization initiator preferably has a 10-hour half-life temperature in water of 30 to 90 ° C, more preferably 30 to 80 ° C. An azo-based polymerization initiator having a 10-hour half-life temperature in water of more than 90 ° C. has a small amount of radicals generated in a preferable polymerization temperature range to be described later, resulting in a long polymerization time or formation of a high-molecular weight copolymer. . Examples of the azo-based polymerization initiator include azonitrile compounds, azoamidine compounds, cyclic azoamidine compounds, azoamide compounds, alkylazo compounds, azobiscyanovaleric acid and salts thereof. Below, the specific example of an azo type polymerization initiator is shown with a 10-hour half-life temperature in water.

Specifically as the azonitrile compound,
2,2′-azobis-2,4-dimethylvaleronitrile (51 ° C.) may be mentioned. Specific examples of the azoamidine compound include 2,2′-azobis (2-amidinopropane) hydrochloride (56 ° C.) and 2,2′-azobis [N-
(2-Carboxyethyl) amidinopropane] (57
℃). Further, specifically, as the cyclic azoamidine compound, 2,2′-azobis [2- (5
-Methyl-2-imidazolin-2-yl) propane] hydrochloride (41 ° C), 2,2'-azobis [2- (2-imidazolin-2-yl) propane] hydrochloride (44 ° C),
2,2′-azobis [2- (2-imidazolin-2-yl) propane] sulfate (47 ° C.), 2,2′-azobis [2- (3,4,5-tetrahydropyridin-2-yl) Propane] hydrochloride (58 ° C.), 2,2′-azobis {2- [1- (2-hydroxyethyl) -2-imidazolin-2-yl] propane} hydrochloride (60 ° C.), 2,2
'-Azobis [2- (2-imidazolin-2-yl) propane] (61 ° C) can be mentioned.

As the azoamide compound, specifically, 2,2'-azobis {2-methyl-N- [1,1-
Bis (hydroxymethyl) -2-hydroxyethyl] propionamide} (80 ° C.), 2,2′-azobis {2
-Methyl-N- [2- (1-hydroxybutyl)] propionamide} (85 ° C), 2,2'-azobis [2-
Methyl-N- (2-hydroxyethyl) propionamide] (86 ° C.) and the like. These azo-based polymerization initiators can be used alone or in admixture of two or more.

The amount of the polymerization initiator (d) used is preferably in the range of 0.1 to 6% by weight, more preferably 0.5 to 3% by weight, based on the total amount of the monomers. . When the amount of the polymerization initiator (d) used is less than 0.1% by weight, the amount of unreacted residual monomer is large, and the reaction time becomes long. On the other hand, if the amount exceeds 6% by weight, the amount of radicals generated in the initial stage of polymerization increases, which not only lowers the molecular weight of the resulting copolymer but also increases the cost.

The reaction temperature for radical polymerization of the monomer mixture is preferably in the range of 30 to 90 ° C.,
It is more preferably in the range of 40 to 80 ° C. When the reaction temperature is lower than 30 ° C., the amount of radicals generated in the initial stage of polymerization is small, and thus it takes a long time to complete the polymerization, which is economically disadvantageous. On the other hand, when the temperature exceeds 90 ° C., the amount of radicals generated in the initial stage of polymerization increases, so that the molecular weight of the obtained copolymer becomes low, which may adversely affect the physical properties of the image receiving layer formed using the image receiving coating agent. There is not preferable. The solid content (nonvolatile content) of the obtained copolymer emulsion (A) is preferably 40 to 70% by weight. If the solid content of the copolymer emulsion (A) is less than 40% by weight, the solid content and viscosity of the image-receiving coating agent will be low,
It is difficult to obtain the required film thickness of the image receiving layer. On the other hand, if it exceeds 70% by weight, the viscosity of the obtained copolymer emulsion (A) becomes extremely high and it becomes difficult to mix it with other components constituting the image-receiving coating agent.

The cationic compound (B) contained in the image-receiving coating agent suppresses the bleeding of the recorded image and improves the water resistance when the aqueous recording ink of the present invention is used for printing. is there. Examples of such a cationic compound (B) include amine salts, quaternary ammonium salts, amide compounds, pyridinium salts, imidazolines, and ethylene oxide adducts of higher alkylamines.

Specific examples of the cationic compound are shown below. As the amine salt, lauryl amine, coconut amine,
Examples thereof include hydrochlorides and acetates of primary, secondary or tertiary amines such as stearylamine and rosinamine. Examples of the quaternary ammonium salt include lauryl trimethyl ammonium chloride, lauryl dimethyl benzyl ammonium chloride, benzyl tributyl ammonium chloride, and benzalkonium chloride. Examples of the amide compound include dicyandiamide and its condensate. Examples of the pyridinium salt include cetylpyridinium chloride and cetylpyridinium bromide. The imidazolines include 2-heptadecyl-
Examples thereof include hydroxyethyl imidazoline. Examples of the ethylene oxide adduct of higher alkylamine include dihydroxyethylstearylamine and the like.

Other cationic compounds include polyallylamine hydrochloride, polyamine sulfone hydrochloride, polyvinylamine hydrochloride, chitoacetate acetate, polyethyleneimine, oxazoline polymer, polyvinylpyrrolidone, cationized starch and the like. In addition, a nonionic polymer compound obtained by cationizing a part of the nonionic polymer compound may be used. Specific examples thereof include a copolymer of vinylpyrrolidone and a quaternary salt of aminoalkyl acrylate, a copolymer of acrylamide and a quaternary salt of aminomethyl acrylamide, and the like. These cationic compounds are preferably water-soluble, but may be a dispersion such as latex or emulsion.

The cationic compound (B) is preferably contained in the image receiving coating agent in the range of 10 to 90% by weight based on the solid content of the (meth) acrylamide copolymer emulsion (A). In particular, it is preferably contained in the range of 20 to 50% by weight. When the content of the cationic compound (B) is less than 10% by weight, bleeding may occur due to insufficient ink fixability of the image receiving layer formed using the image receiving coating agent. Also, 90% by weight
When it exceeds, the ink absorbency of the image receiving layer is lowered.

The inorganic filler (C) contained in the image-receiving coating agent functions to improve blocking of the recording sheet, transportability, etc., to appropriately diffuse the ink printed on the image-receiving layer, and to form a high-quality image. Is what you do. Specific examples of the inorganic filler (C) include calcium carbonate, barium sulfate, calcium hydroxide, talc, silica, titanium oxide, zinc oxide, zirconia, metallic fine particles (antimony, etc.), alumina, aluminum silicate, and silicic acid. Examples thereof include magnesium, hydrotalcite, clay, basic magnesium carbonate and the like.

The inorganic filler (C) is preferably contained in the image receiving coating agent in the range of 1 to 80% by weight based on the solid content of the (meth) acrylamide copolymer emulsion (A). In particular, it is preferably contained in the range of 20 to 70% by weight. Content of inorganic filler (C) is 1
If the amount is less than 10% by weight, the effects of preventing blocking and improving the ink absorbability are not sufficiently exhibited, and if it exceeds 80% by weight, the viscosity of the image-receiving coating agent becomes remarkably high and chalking occurs on the surface of the image-receiving layer. .

The same nonionic surfactant or amphoteric surfactant as that used in the synthesis of the (meth) acrylamide copolymer emulsion (A) may be added to the image-receiving coating agent. When such a surfactant is added, the image density is increased and the occurrence of bleeding is further suppressed depending on the ink used for image formation.

As the image-receiving coating agent, the (meth) acrylamide copolymer emulsion (A), the cationic compound (B) and the inorganic filler (C) are uniformly mixed by using a known mixing device such as a homogenizer. It can be prepared by mixing. The solid content of the image-receiving coating agent is 30 to 6
It is preferably in the range of 0% by weight, particularly 35 to 50
It is preferably in the range of% by weight. When the solid content of the image-receiving coating agent is less than 30% by weight, it is not possible to obtain an image-receiving layer having a film thickness necessary for satisfying high-quality inkjet recording characteristics by applying only once in-line in the printing process. In order to satisfy the recording characteristics, it is necessary to apply the image-receiving coating agent a plurality of times. On the other hand, when it exceeds 60% by weight, the viscosity of the image-receiving coating agent becomes high, so that the smoothness of the surface of the image-receiving layer is impaired or chalking occurs.

Next, an ink jet recording sheet prepared by using the above image receiving coating agent will be described. The recording sheet has an image receiving layer formed by using the image receiving coating agent on a sheet base material. As the sheet substrate, a plastic sheet made of polyethylene terephthalate, diacetate, triacetate, cellophane, celluloid, polycarbonate, polyimide, polyvinyl chloride, polyvinylidene chloride, polyacrylate, polyethylene, polypropylene, polycarbonate, polyether sulfone, polyvinyl chloride, or the like. Can be used. In addition, an opaque substrate such as white may be used as long as it is not used for forming a transparent image such as OHP.
It is also possible to use various papers such as synthetic paper, high-quality paper, art paper, coated paper, cast coated paper, paperboard, cloth, non-woven fabric, iron plate, stainless plate, enamel and glass plate.

The base sheet is used in accordance with various conditions such as the purpose of use of the recording sheet, the purpose of recorded image and the adhesion to the image receiving layer.
Select appropriately. The thickness of the base sheet is appropriately selected in consideration of strength depending on the application and is not particularly limited, but is usually about 5 to 200 μm. The surface of the substrate sheet may be subjected to a known easy-adhesion treatment such as corona discharge treatment or formation of an anchor layer made of polyurethane resin or the like in order to improve the adhesiveness of the image receiving layer.

The recording sheet can be prepared by applying an image-receiving coating agent on a sheet base material by a known method and drying it using a hot-air drying oven, a heating drum or the like to form an image-receiving layer. . Known coating methods include, for example, roll coater method, blade coater method, air knife coater method, gate roll coater method, bar coater, spray coat, slit coat method, gravure coater method, flexo coater method, curtain coater method, spin. The coater method and the like can be mentioned. In order to smooth the surface of the image receiving layer or to improve the strength of the surface of the recording sheet,
You may give a super calendar process.

The coating amount (after drying) of the image-receiving coating agent is 0.5 in order to exhibit a sufficient ink absorbing ability.
It is preferably in the range of 50 to 50 g / m ² , particularly 3
It is preferably -40 g / m ² . When the coating amount of the image-receiving coating agent is less than 0.5 g / m ^2, insufficient ink absorbency of the image-receiving layer, there is a risk that deposited ink is either not dried or bleeding occurs, a 50 g / m ² If it exceeds, curling may occur or the image-receiving layer may peel off, resulting in high cost.

[0043]

The present invention will be described below with reference to examples, but the present invention is not limited thereto. In addition, in the synthesis example, Esocard C-25 is a cationic surfactant (95% active ingredient) manufactured by Lion Akzo Co., Ltd., Liponox NC.
-200 is a nonionic surfactant manufactured by Lion (100% active ingredient), V-50 is an azo polymerization initiator manufactured by Wako Pure Chemical Industries (2,2'-azobis (2-amidinopropane)).
Hydrochloride). The viscosity was measured at 25 ° C with a B-type viscometer.

[Synthesis Example 1] 122.5 g of water was charged into a four-necked flask equipped with a thermometer, a reflux condenser and a nitrogen introducing tube, and after nitrogen substitution, the temperature was raised to 80 ° C. "V-50"
A mixture of 2.2 g and 19.4 g of water was added to the flask,
Subsequently, 107.5 g of n-butyl methacrylate, 107.5 g of N-methylolacrylamide, 6.5 g of sodium hypophosphite monohydrate, and "Esocard C-25" 21.5.
g, "Liponox NC-200" 8.6 g and water 9
5.7 g of the mixture was continuously added dropwise in about 2 hours. After the completion of dropping, the mixture was kept for 2 hours under the same conditions and then cooled and taken out. Solid content 50.2% by weight, pH 4.9, viscosity 350 m
A Pa.S copolymer emulsion was obtained.

[Synthesis Example 2] A four-necked flask equipped with a thermometer, a reflux condenser and a nitrogen introducing tube was charged with 12 parts of water.
After charging 2.5 g of nitrogen, the temperature was raised to 80 ° C. "V
-50 "2.2 g of water and 19.4 g of water are added to the flask, followed by n-butyl methacrylate 107.5.
g, methyl methacrylate 107.5 g, sodium hypophosphite monohydrate 6.5 g, "Esocard C-25" 21.5
g, "Liponox NC-200" 8.6 g and water 9
5.7 g of the mixture was continuously added dropwise in about 2 hours. After the completion of the dropping, the mixture was kept for 2 hours under the same conditions and then cooled and taken out to obtain a solid content of 49.9% by weight, a pH of 5.1 and a viscosity of 370 m.
A Pa.S copolymer emulsion was obtained.

[Synthesis Example 3] From Synthesis Example 1, only sodium hypophosphite monohydrate was removed, and the other components were prepared in the same manner.
A copolymer emulsion of 9.6% by weight, pH 4.9 and viscosity 9200 mPa · S was obtained.

Example 1 50 g of the copolymer emulsion of Synthesis Example 1, an aqueous solution of a dicyandiamide condensate (“Paracon PJ-O” manufactured by Ohara Palladium Co., solid content 25% by weight,
Weight average molecular weight of the condensate: 1000) 19 g and water 1
2.5 g was mixed, and further 4.8 g of finely powdered silica (“FINESEAL X-45” manufactured by Tokuyama Corp.) was mixed to obtain an image-receiving coating agent having a solid content of 40% by weight. This image-receiving coating agent is applied on an art-coated paper (“NK special piece art” manufactured by Nippon Paper Industries Co., Ltd., paper thickness: 110 μm) with a coating amount of 15 g after drying.
/ M ² coating using a bar coater, 100 ℃
And dried to prepare an ink jet recording sheet.

[Example 2] 50 g of the copolymer emulsion of Synthesis Example 1, an aqueous solution of a quaternary ammonium salt polymer ("Papiogen P-105" manufactured by Senka Co., solid content 60% by weight, weight average molecular weight of polymer: 20,000). ) 12.5 g and 41.3 g of water were mixed, and further 15 g of finely powdered silica (“FINESEAL X-45” manufactured by Tokuyama Corporation) was mixed to obtain an image-receiving coating agent having a solid content of 40% by weight. This image-receiving coating agent was applied onto an art-coated paper (“NK Special Piece Art” manufactured by Nippon Paper Industries Co., Ltd., paper thickness: 110 μm) so that the coating amount after drying was 15
Coat using a bar coater to 100 g / m ²
An ink jet recording sheet was prepared by drying at ° C.

[Example 3] 50 g of the copolymer emulsion of Synthesis Example 1, an aqueous solution of a quaternary ammonium salt polymer ("Papiogen P-105" manufactured by Senka Co., solid content 60% by weight, polymer weight average molecular weight: 20,000). 21.3 g and 49.4 g of water were mixed, and further 17.5 g of finely powdered silica (“FINESEAL X-45” manufactured by Tokuyama Corporation) was mixed to obtain an image-receiving coating agent having a solid content of 40% by weight. This image-receiving coating agent is applied onto an art-coated paper (“NK Special Piece Art” manufactured by Nippon Paper Industries Co., Ltd., paper thickness 110 μm) at a coating amount of 1 after drying.
Coat using a bar coater to 5 g / m ² and apply 10
An ink jet recording sheet was prepared by drying at 0 ° C.

Example 4 50 g of the copolymer emulsion of Synthesis Example 1, an aqueous solution of a dicyandiamide condensate (“Paracon PJ-O” manufactured by Ohara Palladium Co., solid content 25% by weight,
Weight average molecular weight of condensate: 1000) 30 g and water 3
1.7 g were mixed, and further, 20.3 g of finely powdered silica (“FINESEAL X-45” manufactured by Tokuyama Corporation) was mixed,
An image-receiving coating agent having a solid content of 40% by weight was obtained. This image-receiving coating agent is applied on an art-coated paper (“NK special piece art” manufactured by Nippon Paper Industries Co., Ltd., paper thickness: 110 μm) with a coating amount of 15 g after drying.
/ M ² coating using a bar coater, 100 ℃
And dried to prepare an ink jet recording sheet.

[Example 5] 50 g of the copolymer emulsion of Synthesis Example 1, an aqueous solution of a quaternary ammonium salt polymer ("Papiogen P-105" manufactured by Senka Co., solid content 60% by weight, weight average molecular weight of polymer: 20,000). ) 12.5 g and 80.8 g of water were mixed, and further 15 g of finely powdered silica (“FINESEAL X-45” manufactured by Tokuyama Corporation) was mixed to obtain an image-receiving coating agent having a solid content of 30% by weight. This image-receiving coating agent was applied onto an art-coated paper (“NK Special Piece Art” manufactured by Nippon Paper Industries Co., Ltd., paper thickness: 110 μm) so that the coating amount after drying was 11
Coat using a bar coater to 100 g / m ²
An ink jet recording sheet was prepared by drying at ° C.

Comparative Example 1 50 g of the copolymer emulsion of Synthesis Example 2, an aqueous solution of a quaternary ammonium salt polymer (“Papiogen P-105” manufactured by Senka Co., solid content 60% by weight, weight average molecular weight of polymer: 20,000). ) 12.5 g and 41.3 g of water were mixed, and further 15 g of finely powdered silica (“FINESEAL X-45” manufactured by Tokuyama Corporation) was mixed to obtain an image-receiving coating agent having a solid content of 40% by weight. This image-receiving coating agent was applied onto an art-coated paper (“NK Special Piece Art” manufactured by Nippon Paper Industries Co., Ltd., paper thickness: 110 μm) so that the coating amount after drying was 15
Coat using a bar coater to 100 g / m ²
An ink jet recording sheet was prepared by drying at ° C.

Comparative Example 2 50 g of the copolymer emulsion of Synthesis Example 1 and 35 g of water were mixed, and 15 g of finely powdered silica (“FINESEAL X-45” manufactured by Tokuyama Corporation) was added.
Were mixed to obtain an image-receiving coating agent having a solid content of 40% by weight.
This image-receiving coating agent is applied to art-coated paper (“N
K special piece art ", paper thickness 110 μm) was coated using a bar coater so that the coating amount after drying was 15 g / m ² , and dried at 100 ° C to prepare an inkjet recording sheet. .

[Comparative Example 3] 50 g of the copolymer emulsion of Synthesis Example 1, an aqueous solution of a quaternary ammonium salt polymer ("Papiogen P-105" manufactured by Senka Co., Ltd., solid content 60% by weight, weight average molecular weight of polymer: 20,000). ) 12.5 g and water 18.8 g were mixed to obtain an image-receiving coating agent having a solid content of 40% by weight. This image-receiving coating agent was applied onto an art-coated paper (“NK Special Piece Art” manufactured by Nippon Paper Industries Co., Ltd., paper thickness: 110 μm) using a bar coater so that the coating amount after drying would be 15 g / m ² . An inkjet recording sheet was prepared by drying at 100 ° C.

Comparative Example 4 50 g of the copolymer emulsion of Synthesis Example 3, an aqueous solution of a quaternary ammonium salt polymer ("Papiogen P-105" manufactured by Senka Co., solid content 60% by weight, weight average molecular weight of polymer: 20,000). ) 12.5 g and 41.3 g of water were mixed, and further 15 g of finely powdered silica (“FINESEAL X-45” manufactured by Tokuyama Corporation) was mixed to obtain an image-receiving coating agent having a solid content of 40% by weight. An attempt was made to apply this image-receiving coating agent to art-coated paper, but it could not be applied because the image-receiving coating agent had a very high viscosity and poor fluidity.

An ink jet printer ("PM-8 manufactured by Epson Corporation" was applied to the recording sheets prepared in Examples and Comparative Examples.
20C ") was used for recording, and the water resistance, drying property, bleeding, and image density of the recorded image were evaluated by the following methods. The results are shown in Table 1. (1) CMYK (cyan, recorded with a water-resistant inkjet printer)
A 100% solid portion of each color (magenta, yellow, black) was rubbed back and forth 10 times with a cotton swab soaked in water, and the state was visually evaluated at the following levels. ◎ ・ ・ ・ Extremely good ○ ・ ・ ・ Slightly defective △ ・ ・ ・ Between ○ and × × ・ ・ ・ Remarkable defective

(2) Drying After recording for 30 seconds with an ink jet printer, PPC paper was brought into contact with 100% solid portions of each color of CMYK, and the degree of ink set-off on the PPC paper was visually evaluated. ◎ ・ ・ ・ No set-off ○ ・ ・ ・ Slight set-off △ ・ ・ ・ Intermediate between ○ and ×× ・ ・ ・ Significant set-off

(3) Blurred ink-jet printer recorded purple / superimposed colors
The degree of bleeding was visually evaluated for the edges of 100% solid green / orange. ◎ ・ ・ ・ No bleeding ○ ・ ・ ・ Slight bleeding △ ・ ・ ・ Between ○ and × × ・ ・ ・ Remarkable bleeding (4) Image density 100 CMYK colors recorded by inkjet printer
% The density of the solid area is measured by a reflection densitometer (X
-Rite 408G).

[0059]

[Table 1]

[0060]

INDUSTRIAL APPLICABILITY The ink jet recording sheet prepared by using the ink jet image-receiving coating agent of the present invention has excellent drying characteristics, ink absorbency, bleeding of recorded images, water resistance, and excellent ink jet recording characteristics. I have.

Claims (5)

[Claims] 1. A hydrophilic ethylenically unsaturated monomer (a) containing (meth) acrylamide and / or a derivative thereof.
1) A chain transfer agent (b) consisting of hypophosphorous acid or a salt thereof in an aqueous medium, containing a monomer mixture consisting of 5 to 80% by weight and a hydrophobic ethylenically unsaturated monomer (a2) of 20 to 95% by weight. Emulsion polymerization in the presence of a surfactant (c) and a polymerization initiator (d) (meta)
An ink jet image-receiving coating agent comprising an acrylamide copolymer emulsion (A), a cationic compound (B), and an inorganic filler (C). 2. The content of the cationic compound (B) is in the range of 10 to 90% by weight based on the solid content of the (meth) acrylamide copolymer emulsion (A). Item 1. The ink jet image-receiving coating agent according to Item 1. 3. The content of the inorganic filler (C) is in the range of 1 to 80% by weight based on the solid content of the (meth) acrylamide copolymer emulsion (A). Item 3. The inkjet image-receiving coating agent according to Item 1 or 2. 4. The image-receiving coating agent for inkjet according to any one of claims 1 to 3, which has a solid content of 30 to 60% by weight. 5. An ink jet recording sheet having an image receiving layer formed on the sheet substrate using the ink jet image receiving coating agent according to any one of claims 1 to 4.