JP2006335004A - Inkjet recording sheet and organic particle for use in it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an inkjet recording sheet excellent in ink absorbency, developed color density and ozone resistance, and an organic particle for use in the inkjet recording sheet. <P>SOLUTION: In the inkjet recording sheet in which at least one layer containing the organic particle is provided on a substrate, the organic particle is a multilayered structure with a core part and a shell part; a resin component constituting the core part has non-swelling properties with water of pH 8; and a resin component constituting the shell part has swelling properties with or is dissolved in water of pH 8. The organic particle for use in the inkjet recording sheet is a multilayered structure with a core part and a shell part; a resin component constituting the core part has non-swelling properties with water of pH 8; and a resin component constituting the shell part has swelling properties with water of pH 8, or is dissolved in water of pH 8. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ink jet recording sheet applied to a printer or plotter using an ink jet recording system.

  A recording method called ink jet can obtain an image comparable to printing or photography, and is being widely applied in the field of full-color image recording. In order to record a full-color image, the resolution is improved and the color reproduction range is expanded by increasing the ink ejection amount. Therefore, an increase in the ink absorption capacity corresponding to the ejection amount is an important technical problem of the recording sheet, and ink absorptivity is an important characteristic required for the recording sheet.

  In order to ensure ink absorption, it is desired to provide a coating layer having a large void amount. As a coating composition for forming this coating layer, inorganic particles and a small amount for binding the inorganic particles are used. What consists of a binder is known. Since this coating composition has a small amount of binder, voids are formed between the inorganic particles, and ink absorbability can be secured.

  By forming such a coating layer, it has been possible to improve the ink absorptivity and thereby obtain a high-quality image, but there is still a problem with the storability of the recorded image compared with the photograph. is there. This is considered to be a fading of the recorded image by light or an oxidizing gas such as SOx, NOx, oxygen, ozone, etc. (Generally, the storage stability against light is called light resistance, and the storage stability due to the oxidizing gas. In particular, since ozone gas is generally used for evaluation of gas resistance, the performance is commonly referred to as ozone resistance).

  By the way, in the recording sheet currently widely used, since the coating layer has an increased amount of voids for improving the ink absorbability, there is a problem that the contact with the oxidizing gas increases and the ozone resistance decreases. ing. Further, silica or alumina is usually used as the inorganic particles, but there is a problem that the light resistance and ozone resistance of the recorded image are low because the surface activity of the inorganic particles is high.

  Further, when a gloss is imparted to the surface of the recording paper, the surface is smoothed by imparting a gloss by forming a coating layer by selectively using finer inorganic particles. However, since the surface area increases dramatically as the inorganic particles become finer, there is a problem that the surface activity is further increased, and the light resistance and ozone resistance of the recorded image are further lowered.

  Therefore, it is difficult to obtain an ink jet recording sheet excellent in ink absorbability and ozone resistance by the conventional technology using inorganic particles.

  In order to solve such problems, various improved techniques have been proposed. For example, Japanese Patent Laid-Open No. 7-266689 discloses that a recording medium having excellent ozone resistance can be obtained by using polyallylamine. It is disclosed. This polyallylamine is a water-soluble polymer.

  Japanese Patent Application Laid-Open No. 8-164664 discloses a recording sheet composed of inorganic particles to which cycloamylose is immobilized and a binder. In this recording sheet, ozone resistance is improved by the inclusion of the dye in the ink in cycloamylose.

  Further, JP-A-9-254526 discloses an ink jet recording sheet on which an ink receiving layer using an inorganic sol and a polysiloxane polymer as a binder resin is formed. In this ink jet recording sheet, the polysiloxane polymer, which is an inorganic polymer, is extremely resistant to deterioration due to ozone, ultraviolet rays, etc., so that the image storability is improved.

  Thus, although a recording sheet having improved ozone resistance using a specific organic polymer or inorganic polymer has been proposed, it has not always been satisfactory.

  In order to solve such a problem, the present inventors have at least one layer containing organic particles on a sheet-like support in WO2003 / 6251, and the organic particles have a dry particle size in water. An ink jet recording sheet has been proposed that has a swellability of 5 times or more the particle diameter in the state or is soluble in water. This ink jet recording sheet exhibits excellent ozone resistance because particles are swollen or dissolved by the ink after printing and the voids are blocked, and contact between the outside air and the dye is suppressed.

  This proposal can significantly improve ozone resistance, but with the recent increase in speed and quality of inkjet printers, more ink absorbency is required while maintaining excellent ozone resistance. ing.

JP-A-7-266689 JP-A-8-164664 JP 9-254526 A WO2003 / 6251

An object of the present invention is to provide an ink jet recording sheet that solves the above problems, that is, ozone resistance and ink absorbability.

  As a result of intensive studies, the present inventors have found that the organic particles used in the inkjet recording sheet are a multilayer structure having a core part and a shell part, and the resin component constituting the core part is non-swellable in water at pH 8. If the organic resin particles that swell or dissolve in the pH 8 water component are used as the resin component constituting the shell, surprisingly, the ink jet recording is excellent in ink absorbability and ozone resistance. The present inventors have found that a sheet can be obtained and have completed the present invention.

That is, the present invention
An inkjet recording sheet having at least one layer containing organic particles on a support, wherein the organic particles are a multilayer structure having a core portion and a shell portion, and the resin component constituting the core portion is water having a pH of 8 An ink jet recording sheet that is non-swellable and has a swellable or soluble resin component constituting the shell portion in water having a pH of 8,
And
Organic particles used for an ink jet recording sheet, a multilayer structure having a core portion and a shell portion, the resin component constituting the core portion being non-swellable in water at pH 8, and the resin component constituting the shell portion Are organic particles that swell or dissolve in pH 8 water.

According to the present invention, it is possible to provide an ink jet recording sheet excellent in ink absorbability and ozone resistance, and organic particles used in the recording sheet.

  The ink jet recording sheet of the present invention has at least one layer containing organic particles on a support.

  Since the organic particles in the ink jet recording sheet of the present invention can maintain a particle shape and form voids between the particles in a dry state, the voids are the same as the inorganic particles of silica and alumina used in the prior art. It exhibits a good ink absorbability due to its characteristics. Further, after printing, the particles are swollen or dissolved by the ink to close the voids, and the contact between the outside air and the dye is suppressed, so that excellent ozone resistance is exhibited.

  Details will be described below.

[Organic particles]
The organic particle of the present invention is a multilayer structure having a core part and a shell part, and the resin component constituting the core part is non-swellable in pH 8 water, and the resin component constituting the shell part is pH 8 Organic particles that swell or dissolve in water.

  The phrase “having swellability in pH 8 water” as used in the present invention means that the resin component absorbs alkaline water contained in the ink and the volume is increased by 1.2 times or more. The preferred volume increase rate when swollen is 2 times or more, more preferably 5 times or more. Further, “non-swellable in water at pH 8” means that the resin component hardly absorbs the water and the volume increase rate is less than 1.2 times. The phrase “dissolves in water at pH 8” means that the resin component and water at pH 8 form a single phase in an equilibrium state.

  The weight average particle diameter of the organic particles in the present invention can be measured by a light scattering method. For example, it can be measured with a laser particle size analysis system LPA-3000 / 3100 (Otsuka Electronics Co., Ltd.), a laser diffraction particle size distribution analyzer SALD-2000A (Shimadzu Corporation), or the like.

  In addition, the swelling particle diameter or solubility of organic particles in water is evaluated using water adjusted to pH 8, the temperature of water is 25 ° C., and the immersion time in water is 12 hours.

  The weight average particle diameter of the organic particles of the present invention is usually 20 nm to 1000 nm, preferably 20 nm to 500 nm, more preferably 20 nm to 200 nm in a dry state. When the weight average particle diameter is not less than the above lower limit, the ink absorbability is good, and when the weight average particle diameter is not more than the above upper limit, the total surface area of all organic particles in the same weight increases, so the contact area with the ink is By increasing, sufficient particle swelling or dissolution is obtained, and the effect on ozone resistance is exhibited.

  The resin component constituting the core portion of the organic particles of the present invention is organic particles that are non-swellable in water at pH 8, and in order to have such a function, the composition ratio of the polymer components constituting the core portion However, the structural unit (a) derived from the carboxyl group-containing monomer having a polymerizable double bond is 0 to 9% by weight, and the structural unit (b) derived from another copolymerizable monomer is in the range of 100 to 91% by weight. Preferably, the structural unit (a) derived from a carboxyl group-containing monomer having a polymerizable double bond is 0 to 5% by weight, and the structural unit (b) derived from another copolymerizable monomer is 100 to 5% by weight. % Range.

  When the composition ratio of the polymer component (a) in the resin component of the core part is not more than the above upper limit, the non-swelling property is good, which is preferable.

  The resin component constituting the shell part of the organic particle of the present invention is an organic particle having swelling or solubility in water having a pH of 8, and in order to have such a function, the shell part is constituted. The polymer component composition ratio is such that the structural unit (a) derived from the carboxyl group-containing monomer having a polymerizable double bond is 10 to 60% by weight, and the structural unit (b) derived from another copolymerizable monomer is 90%. The structural unit derived from a carboxyl group-containing monomer having a polymerizable double bond, preferably 15 to 60% by weight, and a structural unit derived from another copolymerizable monomer (b ) Is in the range of 85-40% by weight.

  When the composition ratio of the polymer component (a) in the resin component of the shell part is not less than the above lower limit, the swelling or solubility of the resin component by the ink is good, and the composition ratio of the polymer component (a) is the above lower limit. In the following, the polymerization stability is good and preferred.

  Moreover, it is preferable that the ratio of a core part and a shell part is the range of 95: 5-5: 95 by weight ratio, More preferably, it is the range of 90: 10-10: 90.

  Hereinafter, the monomer components (a) and (b) constituting the organic particles will be specifically described.

Examples of the carboxyl group-containing monomer having a polymerizable double bond (a) include:
Acrylic acid, methacrylic acid, 2-methacryloyloxyethyl succinic acid, 2-methacryloyloxyethyl hexahydrophthalic acid, 2-acryloyloxyethyl succinic acid, 2-acryloyloxyethyl phthalic acid, 2-acryloyloxyethyl Examples include hexahydrophthalic acid, itaconic acid, maleic acid, fumaric acid, maleic anhydride, and fumaric anhydride.
As (a), acrylic acid and methacrylic acid are particularly preferable because they have excellent ozone resistance.

Examples of the other copolymerizable monomer (b) include:
Amino group-containing (meth) acrylate monomer; N, N-dimethylaminoethyl acrylate, N, N-dimethylaminoethyl methacrylate, N, N-dimethylaminopropyl acrylate, N, N-dimethylaminopropyl methacrylate, N, N- aminoalkyl acrylates or aminoalkyl methacrylates such as t-butylaminoethyl acrylate, N, N-t-butylaminoethyl methacrylate, N, N-monomethylaminoethyl acrylate, N, N-monomethylaminoethyl methacrylate; and / or these Quaternary chlorides of methyl halide, ethyl halide, benzyl halide, etc.
Acrylamides; acrylamide, methacrylamide, methylol methacrylamide, methylene bisacrylamide, diacetone acrylamide, maleic acid amide, etc.
Further, it is an acrylic acid alkyl ester monomer and / or a methacrylic acid alkyl ester monomer. Specific examples thereof include acrylic acid esters; methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, t -Butyl acrylate, n-amyl acrylate, isoamyl acrylate, n-hexyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, decyl acrylate, dodecyl acrylate, octadecyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, etc.
Methacrylic acid esters; methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, t-butyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate , Dodecyl methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, etc.
Examples thereof include other alkyl acrylates having 1 to 12 carbon atoms and other methacrylates having 1 to 12 carbon atoms.

  Examples of the hydroxyl group-containing (meth) acrylate monomer include 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl methacrylate. And hydroxyl group-containing acrylates or methacrylates.

And aromatic vinyls such as styrene, 2-methylstyrene, t-butylstyrene, chlorostyrene, vinylanisole, vinylnaphthalene and divinylbenzene;
Vinyl esters such as vinyl acetate and vinyl propionate;
Vinylidene halides such as vinylidene chloride and vinylidene fluoride;
Vinyl chloride, vinyl ether, vinyl ketone, vinyl amide, chloroprene, ethylene, propylene, isoprene, butadiene, chloroprene, vinyl pyrrolidone, 2-methoxyethyl acrylate, 2-ethoxyethyl acrylate, glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether, acrylonitrile, meta Acrylonitrile,
Ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol dimethacrylate, polypropylene glycol dimethacrylate, neopentyl glycol dimethacrylate, 1,3-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neo Pentyl glycol dimethacrylate, polyethylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, tripropylene glycol diacrylate, polypropylene glycol diacrylate, trimethylolpropane trimethacrylate, trimethylolpropane triacrylate, tetramethylol Methanetri Acrylate, tetramethylolmethane tetraacrylate, allyl methacrylate, dicyclopentenyl acrylate, dicyclopentenyl oxyethyl acrylate, isopropenyl-.alpha., alpha-dimethylbenzyl isocyanate, allyl mercaptan,
2- (2′-hydroxy-5′-methacryloyloxyethylphenyl) -2H-benzotriazole, 2- (2′-hydroxy-5′-methacryloyloxyphenyl) -benzotriazole, 2-hydroxy-4- (2- And methacryloyloxy) ethoxybenzophenone and 2- (2′-hydroxy-5′-methacryloyloxyphenyl) -5-chlorobenzotriazole.

One or two or more of these can be selected as the monomer (b). The monomer represented by (b) is more preferably a monomer represented by styrene and the following general formula (Formula 1).

[Wherein, R represents a hydrogen atom or a methyl group, and X represents a methyl group, an ethyl group, an n-butyl group, an i-butyl group, a t-butyl group, or an isobornyl group. ]

[Glass Transition Temperature (Tg) of Organic Particles]
As glass transition temperature of the organic particle of this invention, 40 degreeC or more is preferable, More preferably, it is 60 to 250 degreeC, More preferably, it is 60 to 200 degreeC. When the glass transition temperature is equal to or higher than the above lower limit, the organic particles are hardly deformed and fine interparticle voids can be maintained, so that excellent ink absorbability can be obtained.

  In addition, the glass transition temperature (Tg) in this invention is computable from the formula of Fox (FOX) by mass fraction from Tg and monomer composition ratio of the monomer homopolymer as a copolymerization component. . Regarding Tg of monomer homopolymer, many measured values are published in POLYMER HANDBOOK (A WILEY-INTERSCIENCE PUBLICATION).

[Method for producing organic particles]
The organic particles of the present invention can be produced based on a known emulsion polymerization method or mechanical emulsification method. For example, in the emulsion polymerization method, there are a method in which various monomers are charged in a batch in the presence of a dispersant and an initiator, and a method in which polymerization is performed while monomers are continuously supplied. The polymerization temperature at that time is usually 30 to 90 ° C., and a substantially water dispersion system of organic particles generally called an emulsion is obtained. The aqueous dispersion of organic particles obtained by the emulsion polymerization method is excellent in that it is very stable with a small amount of a dispersant and a particle having a very small particle diameter can be easily obtained.

  Examples of the dispersant preferably used here include anionic surfactants, cationic surfactants, amphoteric surfactants, nonionic surfactants, water-soluble polymers, and the like. The above can be selected. These will be described in detail below.

  Specific examples of anionic surfactants include, for example, sodium dodecylbenzenesulfonate, sodium lauryl sulfate, sodium alkyldiphenyl ether disulfonate, sodium alkylnaphthalenesulfonate, sodium dialkylsulfosuccinate, sodium stearate, potassium oleate, sodium dioctyl Sulfosuccinate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl ether sulfate, sodium polyoxyethylene alkyl phenyl ether sulfate sodium dialkyl sulfosuccinate, sodium stearate, sodium oleate, tert-octylphenoxyethoxy polyethoxyethyl sulfate A sodium salt etc. are mentioned.

  Specific examples of the cationic surfactant include lauryltrimethylammonium chloride, stearyltrimethylammonium chloride, cetyltrimethylammonium chloride, distearyldimethylammonium chloride, and alkylbenzyldimethylammonium chloride.

Specific examples of amphoteric surfactants include, for example,
Examples thereof include lauryl betaine, stearyl betaine, lauryl dimethylamine oxide, lauryl carboxymethylhydroxyethyl imidazolinium betaine, coconut amine acetate, stearyl amine acetate, alkyl ammine anidine polyoxyethanol, alkyl picolinium chloride and the like.

  Specific examples of the nonionic surfactant include, for example, polyoxyethylene lauryl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene oleyl phenyl ether, polyoxyethylene nonyl phenyl ether, oxyethylene / oxypropylene block copolymer, tert- Examples include octylphenoxyethyl polyethoxyethanol, nonylphenoxyethyl polyethoxyethanol, and the like.

  Specific examples of the water-soluble polymer include polyvinyl alcohol, polyvinyl pyrrolidone, modified polyvinyl alcohol and the like.

  The amount of the dispersant used is not particularly limited, but is usually 0.02 to 10% by weight, more preferably 0.02 to 5% by weight, and most preferably 0.02 to 3% based on the total weight of the monomers to be copolymerized. % By weight.

  As the initiator used for polymerization, a normal radical initiator can be used, for example, hydrogen peroxide; persulfates such as ammonium persulfate and potassium persulfate; cumene hydroperoxide, t-butyl hydroperoxide, benzoyl Organic peroxides such as peroxide, t-butylperoxy-2-ethylhexanoate, t-butylperoxybenzoate, lauroyl peroxide; azobisisobutyronitrile, 2,2′-azobis (2-amidino Propane) dihydrochloride, 2,2′-azobis [2- (N-phenylamidino) propane] dihydrochloride, 2,2′-azobis {2- [N- (4-chlorophenyl) amidino] propane} dihydrochloride 2,2′-azobis {2- [N- (4-hydroxyphenyl) amidino] propane} dihydrochloride, 2, '-Azobis [2- (N-benzylamidino) propane] dihydrochloride, 2,2'-azobis [2- (N-allylamidino) propane] dihydrochloride, 2,2'-azobis {2- [N -(2-hydroxyethyl) amidino] propane} dihydrochloride, 2,2′-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) -2-hydroxyethyl] propionamide}, 2, 2′-azobis {2-methyl-N- [1,1-bis (hydroxymethyl) ethyl] propionamide}, 2,2′-azobis [2-methyl-N- [2-hydroxyethyl) propionamide], Azo compounds such as 2,2′-azobis (isobutyramide) dihydrate; or these and metal ions such as iron ions and sodium sulfoxylate, formaldehyde, pyrosulfurous Soda, sodium bisulfite, L- ascorbic acid, include redox initiators in combination with reducing agents such as Rongalite is able to select these one or two or more kinds.

  A common initiator is used in an amount of 0.01 to 5% by weight based on the total weight of monomers to be copolymerized.

  If necessary, mercaptans such as t-dodecyl mercaptan and n-dodecyl mercaptan, allyl sulfonic acid, methallyl sulfonic acid and allyl compounds such as soda salts thereof can be used as molecular weight regulators. is there. By using these chain transfer agents, it is possible to adjust the molecular weight of the organic particles, and the amount and type of the organic particles can be appropriately selected so as to be excellent in water swellability or solubility.

  The method for obtaining a multilayer structure having a core part and a shell part, which is a feature of the organic particles of the present invention, is obtained by completing the polymerization reaction of the organic particles constituting the core part in advance and then in the presence of the organic particles. Can be obtained by a seed emulsion polymerization method in which the components constituting are polymerized.

[Support]
In the present invention, the support is a support conventionally used for an inkjet recording sheet, for example, plain paper, art paper, coated paper, cast coated paper, resin-coated paper, resin-impregnated paper, non-coated paper, coated paper. Paper support such as industrial paper, paper support coated on both sides or one side with polyolefin such as polyethylene kneaded with white pigment such as polyethylene and / or titanium, plastic support, nonwoven fabric, cloth, woven fabric, metal film, metal A plate and a composite support obtained by bonding them together can be used.

  As the plastic support, for example, plastic sheets such as polyethylene, polypropylene, polystyrene, polyethylene terephthalate, polyethylene naphthalate, triacetyl cellulose, polyvinyl chloride, polyvinylidene chloride, polyimide, polycarbonate, cellophane, polynylon, and the like are preferable. used. These plastic supports can be appropriately selected from transparent, translucent and opaque ones depending on the application.

  It is also preferable to use a white plastic film for the support. White plastic supports include small plastics containing white pigments such as barium sulfate, titanium oxide, and zinc oxide, foam plastic supports that are provided with a large number of fine voids to provide opacity, and white A support provided with a layer having a pigment (titanium oxide, barium sulfate) can be used.

  In the present invention, the shape of the support is not limited, but in addition to commonly used film shapes, sheet shapes, plate shapes, etc., cylindrical shapes such as beverage cans, disk shapes such as CD and CD-R, and other complicated shapes What has a shape can also be used as a support.

  Since organic particles are used in the inkjet recording sheet of the present invention, a coating layer that maintains voids between particles similar to inorganic particles can be formed until printing. Furthermore, since the resin component constituting the shell portion of the organic particles is swollen or dissolved by the ink after printing and the interparticle voids are closed, it is considered that the ingress of gas is suppressed and the ozone resistance is excellent. Further, since the non-swellable core portion exists, it is considered that the ink absorbability is also excellent. In the case of inorganic particles, a binder that binds the particles to each other in order to maintain the surface strength is essential, but the binder fills the voids between the particles and lowers the porosity, thereby deteriorating the ink absorbability. become. On the other hand, unlike the inorganic particles, the organic particles of the present invention can be fused only on the surface of the particles to achieve both the interparticle void and the surface strength, so that only the organic particles, that is, the organic particles are contained. Even if the content of the organic particles in the layer is 100% by weight, it has a characteristic different from that of the inorganic particles in that excellent ink absorbability can be maintained.

[Organic particle-containing layer]
In the present invention, at least one layer containing the above organic particles is formed on the support surface.

  The content ratio of the organic particles in the layer containing organic particles is 20 to 100% by weight, more preferably 40 to 100% by weight, and still more preferably 60 to 100% by weight. It is preferable for it to be at least the lower limit because it is excellent in ozone resistance.

  The layer containing organic particles may contain inorganic particles in addition to the organic particles described above. Examples of inorganic particles include light calcium carbonate, heavy calcium carbonate, magnesium carbonate, kaolin, clay, talc, calcium sulfate, barium sulfate, titanium dioxide, zinc oxide, zinc hydroxide, zinc sulfide, zinc carbonate, hydrotalcite. , Aluminum silicate, diatomaceous earth, calcium silicate, magnesium silicate, synthetic amorphous silica, colloidal silica, alumina, colloidal alumina, pseudoboehmite, aluminum hydroxide, ritbon, zeolite, magnesium hydroxide and the like. In order to obtain high porosity and improve ink absorbency, silica and alumina are preferable, and fine particles having a primary particle diameter of 100 nm or less are more preferable.

  When these inorganic particles are contained in the layer containing the organic particles of the present invention, the total amount of inorganic particles is 80 parts by weight or less, preferably 60 parts by weight or less, based on 100 parts by weight of the layer. The amount is preferably 40 parts by weight or less.

  The layer containing the organic particles may be used in combination with various additives and various additives that are usually used in inkjet recording sheets. Examples of the polymer having a binder function include water-soluble polymers such as polyvinyl alcohol, modified polyvinyl alcohol, polyvinyl pyrrolidone, starch, gelatin, and casein.

  Further, examples of water dispersions of water-insoluble polymers include acrylic polymers, styrene-acrylic polymers, MBR polymers, SBR polymers, urethane polymers, epoxy polymers, and EVA polymer water dispersions. .

  When using the polymer which has these binder functions, the usage-amount is preferable 0-40 weight part with respect to 100 weight part of layers containing an organic particle, More preferably, it is 0-30 weight part, More preferably, it is 0-20. Parts by weight. If the amount of the binder is not more than the above upper limit, it is preferable because the ink absorbability is good.

  Furthermore, it is also possible to contain a cationic water-soluble polymer for the purpose of improving water bleed resistance and color density.

  Examples of cationic water-soluble polymers include cationized polyvinyl alcohol, cationized starch, cationized polyacrylamide, cationized polymethacrylamide, polyamide polyurea, polyethyleneimine, allylamine or a copolymer thereof, and epichlorohydrin-dialkylamine. Polymer, polymer of diallylalkylamine or a salt thereof, polymer of diallyldialkylammonium salt, diallylamine or a salt thereof and sulfur dioxide copolymer, diallyldialkylammonium salt-sulfur dioxide copolymer, diallyldialkylammonium salt and diallylamine Or a copolymer with a salt or derivative thereof, a polymer of a dialkylaminoethyl acrylate quaternary salt, a polymer of a dialkylaminoethyl methacrylate quaternary salt, a diallyl dialkyl Ammonium salt - acrylamide copolymer, amine - carboxylic acid copolymer and the like.

  In addition, the layer containing the organic particles of the present invention includes an antistatic agent, an antioxidant, a dry paper strength enhancer, a wet paper strength enhancer, a water resistant agent, an antiseptic, an ultraviolet absorber, and a light stabilizer. Agent, fluorescent whitening agent, colored pigment, coloring dye, penetrant, foaming agent, mold release agent, foam suppressor, antifoaming agent, fluidity improver, thickener, pigment dispersant, cationic fixing agent, etc. May be included.

[Configuration of recording sheet]
A preferred configuration example of the ink jet recording sheet in the present invention is that a layer containing organic particles is used as a layer related to ink reception. For example, a single layer structure in which only a layer containing organic particles is provided on a support, a method in which an ink receiving layer is provided on a support, and a layer containing organic particles according to the present invention is provided thereon, the present invention A multilayer structure or the like constituted by providing another layer on the upper layer after providing the organic particle-containing layer. Among them, the case where an ink receiving layer is provided on a support and the layer containing the organic particles according to the present invention is formed on the upper layer of the ink receiving layer is particularly preferable because of excellent gas resistance.

The amount of the layer containing the organic particles of the present invention is usually 0.1 to 50 g / m ² as a basis weight on the sheet-like support, but is not particularly limited.

[Recording sheet manufacturing method]
In the ink jet recording sheet of the present invention, an ink receiving layer is provided on a support or on a support, and a coating composition is applied to the layer containing the organic particles of the present invention on the support, and this is dried to form a layer Can be manufactured. There is no limitation on the application method of the coating liquid, for example, air knife coater, roll coater, bar coater, blade coater, slide hopper coater, gravure coater, flexographic gravure coater, curtain coater, extrusion coater, floating knife coater, comma coater, A conventionally known coating method such as a die coater can be used, followed by drying.

  Examples of the present invention will be described below, but the present invention is not limited to these examples. Moreover, the part and% shown in an Example show a weight part and weight% unless otherwise indicated.

<Production of organic particles>
[Production Example 1: Production of organic particle dispersion (A1)]
513.4 parts of deionized water and 1.5 parts of sodium lauryl sulfonate were charged into a reaction vessel, heated to 70 ° C. under a nitrogen stream, and 1.7 parts of ammonium persulfate was added. Separately, 160.5 parts of styrene, 160.5 parts of t-butyl methacrylate, 17.1 parts of 2-hydroxyethyl methacrylate, and 3.4 parts of divinylbenzene were added to 136.6 parts of deionized water with sodium lauryl sulfonate. An emulsified mixture emulsified using 1.7 parts was prepared, and this emulsified mixture was added dropwise to the reaction vessel in 4 hours. Thereafter, the polymerization was completed by further maintaining at the same temperature for 4 hours.

  As a result, an emulsion composition in which organic particles were dispersed in water with a non-volatile content of 35% and a pH of 3 was obtained.

[Production Example 2: Production of organic particle dispersion (A2)]
689.9 parts of deionized water and 0.97 part of stearyltrimethylammonium chloride were charged into a reaction vessel, heated to 70 ° C. under a nitrogen stream, and then 2,2′-azobis (2-amidinopropane) dihydrochloride 0 97 parts were added. Separately, 91.3 parts of styrene, 91.3 parts of t-butyl methacrylate, 9.7 parts of 2-hydroxyethyl methacrylate, and 1.9 parts of divinylbenzene were added to 77.7 parts of deionized water and stearyltrimethylammonium chloride. An emulsified mixture emulsified with 3.5 parts was prepared, and this emulsified mixture was dropped into the reaction vessel in 4 hours. Thereafter, the polymerization was completed by further maintaining at the same temperature for 4 hours.

  As a result, an emulsion composition in which organic particles were dispersed in water with a non-volatile content of 20% and a pH of 3 was obtained.

[Production Example 3: Production of organic particle dispersion (A3)]
After charging 333.1 parts of the organic particle dispersion (A1) obtained in Production Example 1 as seed particles into 613.1 parts of deionized water, the temperature was raised to 70 ° C. under a nitrogen stream, Two parts were added. Separately, 21.8 parts of methyl methacrylate, 5.5 parts of butyl acrylate, 6.9 parts of methacrylic acid and 0.2 part of n-todecyl mercaptan were added to 13.7 parts of deionized water. An emulsified mixture emulsified using 2 parts was made, and this emulsified mixture was added dropwise to the reaction vessel in 4 hours. Thereafter, the polymerization was completed by further maintaining at the same temperature for 4 hours.

  As a result, an emulsion composition in which organic particles were dispersed in water with a non-volatile content of 15% and a pH of 3 was obtained.

[Production Example 4: Production of organic particle dispersion (A4)]
After charging 333.1 parts of the organic particle dispersion (A1) obtained in Production Example 1 as seed particles into 613.1 parts of deionized water, the temperature was raised to 70 ° C. under a nitrogen stream, Two parts were added. Separately, 15.0 parts of methyl methacrylate, 5.5 parts of butyl acrylate, 13.6 parts of methacrylic acid, and 0.2 part of n-todecyl mercaptan were added to 13.7 parts of deionized water. An emulsified mixture emulsified using 2 parts was made, and this emulsified mixture was added dropwise to the reaction vessel in 4 hours. Thereafter, the polymerization was completed by further maintaining at the same temperature for 4 hours.

  As a result, an emulsion composition in which organic particles were dispersed in water with a non-volatile content of 15% and a pH of 3 was obtained.

[Production Example 5: Production of organic particle dispersion (A5)]
After charging 332.5 parts of the organic particle dispersion (A2) obtained in Production Example 2 as seed particles in 612.5 parts of deionized water, the temperature was raised to 70 ° C. under a nitrogen stream, and then 2,2 ′ -0.2 part of azobis (2-amidinopropane) dihydrochloride was added. Separately, 21.8 parts of methyl methacrylate, 5.5 parts of butyl acrylate, 6.9 parts of methacrylic acid, 0.2 part of n-todecyl mercaptan in 13.4 parts of deionized water 0 An emulsified mixture emulsified using 2 parts was made, and this emulsified mixture was added dropwise to the reaction vessel in 4 hours. Thereafter, the polymerization was completed by further maintaining at the same temperature for 4 hours.

  As a result, an emulsion composition in which organic particles were dispersed in water with a non-volatile content of 15% and a pH of 3 was obtained.

[Production Example 6: Production of organic particle dispersion (A6)]
582.1 parts of deionized water and 0.9 part of sodium lauryl sulfonate were charged into a reaction vessel, heated to 70 ° C. under a nitrogen stream, and then 1.5 parts of ammonium persulfate was added. Separately, 188.6 parts of methyl methacrylate, 47.2 parts of butyl acrylate, 58.9 parts of methacrylic acid and 1.5 parts of n-todecyl mercaptan were added to 117.9 parts of deionized water soda lauryl sulfonate 1 An emulsified mixture emulsified with 5 parts was made, and this emulsified mixture was added dropwise to the reaction vessel in 4 hours. Thereafter, the polymerization was completed by further maintaining at the same temperature for 4 hours.

  As a result, an emulsion composition in which organic particles were dispersed in water with a non-volatile content of 30% and a pH of 3 was obtained.

[Production Example 7: Production of organic particle dispersion (A7)]
After charging 333.1 parts of the organic particle dispersion (A1) obtained in Production Example 1 as seed particles into 613.1 parts of deionized water, the temperature was raised to 70 ° C. under a nitrogen stream, Two parts were added. Separately, 21.8 parts of methyl methacrylate, 5.5 parts of butyl acrylate, 6.9 parts of styrene, 0.2 part of n-todecyl mercaptan in 0.17 parts of deionized water, 0. An emulsified mixture emulsified using 2 parts was prepared, and this emulsified mixture was added dropwise to the reaction vessel in 4 hours. Thereafter, the polymerization was completed by further maintaining at the same temperature for 4 hours.

  As a result, an emulsion composition in which organic particles were dispersed in water with a non-volatile content of 15% and a pH of 3 was obtained.

<Preparation of inkjet recording sheet>
[Preparation of coating liquid (B1)]
First, an aqueous dispersion containing gas phase method silica (Aerosil 200; manufactured by Nippon Aerosil Co., Ltd.) was dispersed as a coating liquid for an inkjet ink receiving layer using a high-pressure homogenizer. Next, 4 parts of dimethyldiallylammonium chloride polycondensate (Charol DC902P; manufactured by Daiichi Kogyo Seiyaku Co., Ltd.) and polyvinyl alcohol (PVA235; manufactured by Kuraray Co., Ltd.) with respect to 100 parts of vapor phase method silica contained in this dispersion. 20 parts and 4 parts of boric acid were added to obtain a coating solution (B1) having a solid content of 12%.

[Preparation of inkjet ink receiving sheet (C1)]
On a paper support (thickness 230 μm) coated on both sides with polyethylene, the coating liquid (B1) is applied and dried to a dry film thickness of 35 μm using a wire bar, and an inkjet ink receiving sheet (C1). Got.

[Example 1]
On the inkjet ink receiving sheet (C1), the organic particle dispersion (A3) obtained in Production Example 3 was applied using a wire bar so that the coating amount was 1 g / m ^{2 in} terms of solid content. It dried and the ink jet recording sheet of Example 1 was obtained.

[Example 2]
In Example 1, it produced by the same method as Example 1 except having changed organic particle dispersion system (A3) into (A4), and the ink jet recording sheet of Example 2 was obtained.

[Example 3]
In Example 1, it produced by the same method as Example 1 except having changed organic particle dispersion system (A3) into (A5), and the ink jet recording sheet of Example 2 was obtained.

[Example 4]
The organic particle dispersion (A5) obtained in Production Example 5, a cationic colloidal silica 20% dispersion (Snowtex AK; manufactured by Nissan Chemical Industries), and polyvinyl alcohol (PVA117; manufactured by Kuraray Co., Ltd.) are solid. It was prepared so that the weight ratio was “87: 10: 3”. The coating liquid thus obtained was applied on the inkjet ink receiving sheet (C1) with a wire bar so that the coating amount was 1 g / m ^{2 in} terms of solid content, and inkjet recording of Example 4 A sheet was obtained.

[Comparative Example 1]
In Example 1, it produced by the same method as Example 1 except having changed organic particle dispersion (A3) into (A6), and the ink jet recording sheet of comparative example 1 was obtained.

[Comparative Example 2]
In Example 1, it produced by the same method as Example 1 except having changed organic particle dispersion (A3) into (A7), and the ink jet recording sheet of comparative example 2 was obtained.

[Evaluation methods]
Below, the evaluation method of the obtained organic particle and a recording sheet is described.

<Measurement method of water swellability of organic particles>
First, the particle diameter (weight average particle diameter) when the pH of the organic particle dispersion is adjusted to pH 3 is (n1), and then the particle diameter (weight average) is adjusted to pH 8 using a 1% aqueous sodium hydroxide solution. From the particle diameter (n2), the volume swelling ratio (m1) of the resin component was calculated according to the following formula 1.

Volume swelling ratio (m1) = (n2 ³ / n1 ³ )

  Further, when the organic particles at this time are a multilayer structure, the particle diameter when the pH of the organic particle dispersion system of the particles constituting the core part is adjusted to pH 3 is (n3), and the resin component of the particles constituting the core part The swelling ratio (m2) of the resin component constituting the shell portion was calculated according to the following formula 2.

Shell part swelling ratio (m2) = (n2 ³ −m1 · n1 ³ ) / (n1 ³ −m1 · n1 ³ )

  Moreover, when the volume of the resin component was not measured, or when (m1 and m2) was 0.1 or less, it was determined that the resin component was dissolved.

  The particle size was measured using a laser particle size analysis system LPA-3000 / 3100 (Otsuka Electronics Co., Ltd.).

<Method for measuring ionicity of organic particles>
The zeta potentials of the organic particle dispersion of the present invention adjusted to pH 3 and those adjusted to pH 8 using a 1% aqueous sodium hydroxide solution were measured. When the zeta potential in water at this time was 0 mV or more (+), it was “cationic”, and when the zeta potential was 0 mV or less (−), it was “anionic”.

  In addition, the zeta potential measurement in this specification can be measured by Zeta Potential / ParticleSizer 380ZLS (manufactured by NICOMP) or the like.

<Measurement method of ink absorbency>
Using a commercially available inkjet printer (PM950C; manufactured by Seiko Epson Corporation), each color of yellow, magenta, cyan, and black was printed in the vertical direction. Immediately after being ejected from the printer, the PPC paper was pressed onto the top, and the ink was The degree of transfer to the PPC paper was visually evaluated. The evaluation criteria are as follows.

A: There is no ink transfer, and the ink absorbency is excellent.
A: Almost no ink transfer and excellent ink absorbency.
Δ: Ink is transferred but within practical limits.
X: Ink is not absorbed at all.

<Measurement method of ozone resistance>
Using a commercially available inkjet printer (PM950C; manufactured by Seiko Epson Corporation), a recording sheet on which solid printing of cyan (model number ICC21: ink pH 8.8) was carried out in a glass container with an ozone inlet and an outlet And stored in an environment with an ozone concentration of 33 ppm for 1.5 hours. The color difference ΔE of the cyan density before storage and after storage was measured using a spectral color difference meter (NF333; manufactured by Nippon Denshoku Industries Co., Ltd.). The evaluation criteria are as follows.

A: ΔE is less than 5 and very excellent in ozone resistance.
○: ΔE is 5 or more and less than 15 and excellent in ozone resistance.
Δ: ΔE is 15 or more and less than 30 and is inferior in ozone resistance.
X: ΔE is 30 or more, and ozone resistance is poor.

  As shown in Table 2, in Examples 1 to 4, excellent ink absorbability and ozone resistance were obtained. On the other hand, in Comparative Example 1, the organic particles were composed only of the water-swellable resin component, and did not satisfy both the ink absorbability and the ozone resistance. Moreover, in the comparative example 2, since the organic particle did not have water swellability, ozone resistance was poor.

An ink jet recording sheet using the organic particles of the present invention is useful as an ink jet recording sheet because of its excellent ink absorbability and excellent ozone resistance.

Claims (5)

An inkjet recording sheet having at least one layer containing organic particles on a support, wherein the organic particles are a multilayer structure having a core portion and a shell portion, and the resin component constituting the core portion is water having a pH of 8 An ink jet recording sheet which is non-swellable and has a swellability or solubility in water having a pH of 8 as a resin component constituting the shell portion. The ink jet recording sheet according to claim 1, wherein the support is a sheet-like support. The polymer constituting the shell part of the organic particles is 10 to 60% by weight of the structural unit (a) derived from the carboxyl group-containing monomer having a polymerizable double bond, and the structural unit derived from another copolymerizable monomer. The inkjet recording sheet according to claim 1, comprising 90 to 40% by weight of (b). Organic particles used for an ink jet recording sheet, a multilayer structure having a core portion and a shell portion, the resin component constituting the core portion being non-swellable in water at pH 8, and the resin component constituting the shell portion Organic particles having a swellability or solubility in water having a pH of 8. The polymer constituting the shell part of the organic particles is 10 to 60% by weight of the structural unit (a) derived from the carboxyl group-containing monomer having a polymerizable double bond, and the structural unit derived from another copolymerizable monomer. The organic particles according to claim 4, comprising 90 to 40% by weight of (b).