JP2008265303A - Ink-jet recording method and recorded matter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology capable of using a conventional ink-jet recording device as it is without additional equipment provided and also a coated paper for printing with low ink absorption as a printing medium. <P>SOLUTION: The ink-jet recording method forms an image by ejecting droplets of an ink compound including at least a colorant, an aqueous organic solvent, a surfactant, and water on a recording medium, the recording media being a regular paper or having a paper support body whose water absorption is 30 ml/m<SP>2</SP>within 30 ms<SP>1/2</SP>from the start of contact by the Bristow method, the ink compound being 15 ng per droplet or less, the water attachment onto the recording medium being 10 mg/inch<SP>2</SP>or less, thereby a recorded matter is obtained. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an inkjet recording method and a recorded matter. More specifically, the present invention relates to an ink jet recording method and recorded matter excellent in cockling or curling characteristics.

  The ink jet recording method is a printing method in which printing is performed by ejecting ink droplets from a printer head and landing on a recording medium such as paper. The ink used in this ink jet recording method needs to have low viscosity in order to fly from the printer head, and ink with a high water content is used. Therefore, inkjet recording paper with high ink absorbability is used as the recording medium.

  According to the inkjet dedicated paper, a high-quality image can be realized. However, if the absorbing layer for absorbing ink is not provided thick, the amount of absorption is reduced, and the amount of coating is increased. In addition, since powdered silica, alumina or the like is used as a raw material to make the absorption layer transparent, the cost has been high. This high cost has become a barrier that narrows the user's applications.

  Although plain paper such as copy paper and coated paper for printing (also referred to as coated paper or main printing paper) are inexpensive, they have lower ink absorbency than ink-jet dedicated paper. For this reason, plain paper is essentially unsuitable as a recording medium for the ink jet recording method. In recent years, various ink-jet recording inks have been developed that guarantee high-quality images even on inexpensive plain paper, but it is extremely difficult to achieve image quality on ink-jet dedicated paper.

  Since the coated paper for printing has a lower ink absorbability than the plain paper, it has been considered to be more inappropriate than the plain paper as a recording medium for the ink jet recording method. However, since the image quality of coated paper is extremely high, a technique for using this as a recording medium for an ink jet recording method has also been proposed.

For example, the print areas P1 and P2 that can be printed in one pass are divided into a plurality of passes for printing, and paper feeding is not performed while printing of the print region is completed in the plurality of passes. There has been proposed an ink jet recording method capable of producing a high-quality image without using additional equipment in a conventional apparatus and using a coated paper for printing having low ink absorbability and excellent printability (Patent Document 1). ).
JP 2006-272732 A

  As described above, combining the advantage of the ink jet recording method, which is simple and small, with the coated paper for printing having low cost and excellent printability has been studied from the viewpoint of the ink jet recording method. There is still room for improvement from the composition point of view.

  Also, when printing on a coated paper for printing using a conventional ink composition having a high water content, wrinkles such as wrinkling of the coated paper after the ink is ejected are generated. There is a problem that a phenomenon such as so-called “curl” occurs in which the coated paper itself warps.

  Accordingly, one of the problems of the present invention is that a conventionally used inkjet recording apparatus can be used as it is without providing any additional equipment, and a coated paper for printing having a low ink absorbency is used as a recording medium. It is to provide the technology used.

In order to achieve the above object, the present invention discharges droplets of an ink composition comprising at least a pigment, a water-soluble organic solvent, a surfactant, and water onto a recording medium to form an image. In the ink jet recording method to be formed, as a recording medium, a recording medium having an absorption layer of a paper support in which water absorption within 30 msec ^1/2 from the start of contact in the Bristow method is 30 ml / m ² or less is used. The ink composition droplets are set to 15 ng or less per droplet, and the water adhesion amount to the recording medium is set to 10 mg / inch ² or less.

  Preferably, droplets of the ink composition are ejected from an ink jet recording head having a single color nozzle density of 360 dpi or more.

  The water content of the ink composition is preferably 10 to 60% by weight.

  Preferably, the water-soluble organic solvent contains at least 15% by weight of (b) a polyhydric alcohol monoalkyl ether having a vapor pressure at 20 ° C. of 0.1 mmHg or less and / or a nitrogen-containing cyclic compound, and (c) Contains polyhydric alcohols. In this case, for example, the ratio of (a) water: (b) polyhydric alcohol monoalkyl ether having a vapor pressure at 20 ° C. of 0.1 mmHg or less and / or nitrogen-containing solvent: (c) content of polyhydric alcohols However, (a) :( b) :( c) = 1: 0.25-8: 0.1-7.

  For example, the pigment concentration is 6% by weight or more in terms of solid content. The pigment is preferably a pigment coated with a water-insoluble polymer or a self-dispersing pigment.

  It is preferable that the surfactant is an acetylene glycol surfactant and / or a poly-modified siloxane surfactant.

  It is preferable that the ink composition further contains a resin emulsion. In this case, the resin emulsion is preferably a mixture of resin fine particles having a minimum film-forming temperature of 20 ° C. or higher and resin fine particles having a minimum film-forming temperature of less than 20 ° C.

  The present invention relates to a recorded matter recorded by the above-described inkjet recording method.

[Inkjet recording method]
Next, the ink jet recording method of the present invention will be described based on preferred embodiments. As described above, the ink jet recording method of the present invention ejects droplets of an ink composition comprising at least a pigment, a water-soluble organic solvent, a surfactant, and water onto a recording medium to form an image. In the inkjet recording method for forming the recording medium, a recording medium having a paper support absorbing layer having a water absorption of 30 ml / m ² or less within 30 msec ^1/2 from the start of contact in the Bristow method is used as the recording medium. The ink composition droplets used are 15 ng or less per droplet, and the amount of moisture adhering to the recording medium is 10 mg / inch ² or less.

  The ink jet recording method of the present embodiment is useful when applied to a recording medium having an absorption layer of plain paper or a paper support with poor ink absorption as the recording medium.

  In the present embodiment, “plain paper” generally refers to paper that uses pulp as a main raw material and is used in a printer or the like, and is defined by JIS P 0001 number 6139. Specific examples include high-quality paper, PPC copy paper, and non-coated printing paper. As the plain paper, those commercially available from various companies can be used. For example, various papers such as Xerox 4200 (manufactured by Xerox) and GeoCycle (Gerogia-Pacific) can be used.

In the present embodiment, “a recording medium having a paper support absorbing layer with poor ink absorption” means that the water absorption within 30 msec ^1/2 from the start of contact in the Bristow method is 30 ml / m ² or less. A recording medium having an absorption layer of a paper support. In the present embodiment, any coated coated paper (printing paper) conventionally used as printing paper for letterpress printing, flat printing (for example, offset printing), or intaglio printing (for example, gravure printing). Can also be used. The printing coated paper includes ordinary coated paper, cast coated paper, and matte coated paper. Also included are printing paper defined by JIS P 0001 number 6122, coated paper defined by JIS P 0001 number 6059 (for example, OK top coat N), and the like.

  The droplets of the ink composition are 15 ng or less per droplet. By setting the ink composition droplets to 15 ng or less per droplet, the fixability of the ink composition can be improved.

  The liquid composition of the ink composition is preferably ejected from an ink jet recording head having a nozzle density of one color of 360 dpi or more. This makes it easy to adjust the appropriate amount of the ink composition to the appropriate range.

In this embodiment, the amount of moisture adhering to the recording medium is 10 mg / inch ² or less. By setting the amount of moisture adhering to the recording medium to 10 mg / inch ² or less, cockling and fixability can be improved.

  The amount of water adhering to the recording medium can also be adjusted by defining the water content of the ink composition. In order to obtain the above water adhesion amount, for example, the water content of the ink composition used in the ink jet recording method of the present embodiment is preferably 10 to 60% by weight. By defining the water content in the ink composition within the above range, the amount of water absorbed by the cellulose in the coated paper is less than in conventional ink compositions, resulting in cockling and curling. It is possible to suppress swelling of cellulose, which is considered to be. Therefore, the ink composition of the present embodiment is also useful for a recording medium having an absorbent layer of a paper support having low ink absorbability, such as plain paper and printing coated paper (printing paper).

[Ink composition]
As described above, the ink composition used in the ink jet recording method according to this embodiment comprises at least a pigment, a water-soluble organic solvent, a surfactant, and water. Hereinafter, each component will be described in detail.

[Pigment]
The colorant of the ink composition used in the present embodiment uses a pigment from the viewpoint of light resistance. As the pigment, both inorganic pigments and organic pigments can be used.

  As inorganic pigments, carbon blacks (CI pigment black 7) such as furnace black, lamp black, acetylene black, channel black, iron oxide, titanium oxide, and the like can be used.

  Organic pigments include insoluble azo pigments, condensed azo pigments, azo lakes and chelate azo pigments, phthalocyanine pigments, perylene and perinone pigments, anthraquinone pigments, quinacridone pigments, dioxane pigments, thioindigo pigments, isoindolinone pigments, and quinophthalone pigments. Polycyclic pigments, dye chelates (eg, basic dye chelate, acid dye chelate), dyeing rake (basic dye rake, acid dye rake), nitro pigment, nitroso pigment, aniline black, daytime Examples thereof include photofluorescent pigments. The above pigments can be used alone or in combination of two or more.

  Carbon black is preferred as the pigment used in the black ink composition. Specific examples of carbon black include # 2300, # 900, HCF88, # 33, # 40, # 45, # 52, MA7, MA8, MA100, # 2200B manufactured by Mitsubishi Chemical, Raven 5750, 5250 manufactured by Columbia, and the like. , 5000, 3500, 1255, 700, etc., Regal 400R, 330R, 660R, Mogu L, 700, Monarch 800, 880, 900, 1000, 1100, 1300, manufactured by Cabot Corporation , 1400, etc. Color Black FW1, FW2V, FW18, FW200, Color Black S150, S160, S170, Printex 35, U, V, 140U, Special Black 6, 5 4A, same Etc. can be mentioned, may be used as these one or a mixture of.

  The color ink composition used in this embodiment preferably includes at least a yellow ink composition, a magenta ink composition, and a cyan ink composition. Examples of the pigment of the color ink composition include pigment yellow, pigment red, pigment violet, pigment blue and the like described in the color index.

  Specifically, for example, C.I. I. Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42, 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104, 108, 109, 110, 117, 120, 128, 138, 147, 150, 153, 155, 174, 180, 188, 198; I. Pigment red 1,3,5,8,9,16,17,19,22,38,57: 1,90,112,122,123,127,146,184,202,207,209; I. Pigment Bio Red 1,3,5: 1, 16, 19, 23, 38; I. Pigment Blue 1, 2, 15, 15: 1, 15: 2, 15: 3, 15: 4, 16; I. Pigment Black 1, 7, etc., and an ink composition can also be formed using a plurality of pigments.

  In particular, the organic pigment contained in the yellow ink composition is C.I. I. Pigment Yellow 74, 109, 110, 128, 138, 147, 150, 155, 180, and 188, and the organic pigment contained in the magenta ink composition includes C.I. I. Pigment red 122, 202, 207, 209, C.I. I. An organic pigment containing at least one selected from Pigment Violet 19 and contained in the cyan ink composition is C.I. I. It is preferable to include at least one selected from CI Pigment Blue 15, 15: 1, 15: 2, 15: 3, 15: 4, and 16.

  Further, any pigment not described in the color index can be used as long as it is insoluble in water.

  The concentration of the pigment may be appropriately determined, but from the viewpoint of the optical density (OD value) in plain paper, it is preferably 6% by weight or more in terms of solid content in the ink composition.

[Pigment covered with water-insoluble polymer]
The pigment used in the ink composition is preferably a pigment coated with at least a water-insoluble polymer. The water-insoluble polymer is composed of a block copolymer resin of a monomer having a hydrophobic group and a monomer having a hydrophilic group, and contains at least a monomer having a salt-forming group. A polymer having a solubility of less than 1 g with respect to 100 g.

  Monomers having hydrophobic groups are methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, isoamyl methacrylate, n-hexyl methacrylate, 2-ethylhexyl methacrylate, octyl methacrylate, decyl methacrylate, dodecyl. Methacrylic acid esters such as methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, glycidyl methacrylate, vinyl esters such as vinyl acetate, vinylcyan compounds such as acrylonitrile, methacrylonitrile, styrene, α-methylstyrene, Vinyltoluene, 4-t-butylstyrene, chlorost Emissions, vinyl anisole, include aromatic vinyl monomers such as vinyl naphthalene, may also be used alone, or a combination of two or more kinds.

  Examples of the monomer having a hydrophilic group include polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, and ethylene glycol / propylene glycol monomethacrylate. These can be used alone or in admixture of two or more. In particular, polyethylene glycol (2-30) monomethacrylate, polyethylene glycol (1-15) / propylene glycol (1-15) monomethacrylate, polypropylene glycol (2-30) methacrylate, methoxypolyethylene glycol (2-30) methacrylate, methoxy Glossiness of a printed image is improved by using a monomer component constituting a branched chain such as polytetramethylene glycol (2-30) methacrylate and methoxy (ethylene glycol / propylene glycol copolymer) (1-30) methacrylate. .

  Monomers having a salt-forming group include acrylic acid, methacrylic acid, styrene carboxylic acid, maleic acid, etc., and each can be used alone or in combination of two or more.

  Furthermore, a macromonomer such as a styrene macromonomer or a silicone macromonomer having a polysynthetic functional group at one end, or other monomers can be used in combination.

  The water-insoluble polymer can be obtained by copolymerizing monomers by a known polymerization method such as a bulk polymerization method, a solution polymerization method, a suspension polymerization method, an emulsion polymerization method, and the solution polymerization method is particularly preferable. In the polymerization, a known radical polymerization agent or polymerization chain transfer agent may be added.

  For example, a pigment coated with a water-insoluble polymer may be prepared by dissolving the water-insoluble polymer in an organic solvent such as methanol, ethanol, isopropanol, n-butanol, acetone, methyl ethyl ketone, or dibutyl ether, and adding the pigment to the resulting solution. Then, a neutralizing agent and water are added and kneaded and dispersed to prepare an oil-in-water dispersion, and an organic solvent is removed from the resulting dispersion to obtain an aqueous dispersion. be able to. For the kneading and dispersing treatment, for example, a ball mill, a roll mill, a bead mill, a high-pressure homogenizer, a high-speed stirring type disperser, or the like can be used.

  The neutralizing agent is preferably a tertiary amine such as ethylamine or trimethylamine, lithium hydroxide, sodium hydroxide, potassium hydroxide, ammonia or the like, and the pH of the resulting aqueous dispersion is preferably 6-10.

  Further, the water-insoluble polymer to be coated is preferably one having a weight average molecular weight of about 10,000 to 150,000 from the viewpoint of stably dispersing the pigment. The weight average molecular weight can be measured by a molecular weight analysis method by gel permeation chromatography (GPC).

  As the pigment coated with the water-insoluble polymer, existing pigments described in “Dye Handbook” (publisher: Maruzen Co., Ltd.) and the like can be used. As the pigment, any of known inorganic pigments and organic pigments can be used. In addition to pigments such as pigment yellow, pigment red, pigment violet, pigment blue, and pigment black described in the color index, phthalocyanine-based, azo Examples thereof include pigments such as azomethine, anthraquinone, azomethine, and condensed ring systems.

  Further, organic pigments such as yellow No. 4, 5, 205, 401; orange 228, 405; blue No. 1, 404, etc., titanium oxide, zinc oxide, zirconium oxide, iron oxide, ultramarine blue, bitumen, Examples thereof include inorganic pigments such as chrome oxide. For example, C.I. I. Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42, 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104, 108, 109, 110, 117, 120, 128, 138, 150, 153, 155, 174, 180, 198, C.I. I. Pigment Red 1,3,5,8,9,16,17,19,22,38,57: 1,90,112,122,123,127,146,184,202,209, C.I. I. Pigment Bio Red 1,3,5: 1, 16, 19, 23, 38, C.I. I. Pigment Blue 1, 2, 15, 15: 1, 15: 2, 15: 3, 15: 4, 16, C.I. I. Pigment Black 1, 7, etc., and an ink composition can also be formed using a plurality of pigments.

[Self-dispersing pigment]
As the pigment used in the ink composition, a self-dispersing pigment can be preferably used instead of the pigment coated with the above-mentioned water-insoluble polymer. “Self-dispersing pigment” refers to a large number of hydrophilic functional groups and / or salts thereof (hereinafter referred to as dispersibility-imparting groups) directly or indirectly via an alkyl group, alkyl ether group, aryl group or the like on the pigment surface. Are pigments that are bound together and can be dispersed and / or dissolved in an aqueous medium without a dispersant. Here, “dispersed and / or dissolved in an aqueous medium without a dispersing agent” means that it is stably present with a minimum particle size that can be dispersed in an aqueous medium without using a dispersing agent for dispersing the pigment. The state refers to the “minimum particle size that can be dispersed” refers to the particle size of the pigment that does not become smaller even if the dispersion time is increased.

  An ink containing a self-dispersing pigment as a colorant does not need to contain a dispersant as described above that is contained in order to disperse a normal pigment. Excellent ink is easy to prepare. In addition, since a significant increase in viscosity due to the dispersant can be suppressed, it is possible to contain more pigment, and the print density can be sufficiently increased.

Self-dispersing pigments are obtained by, for example, applying —COOH, —CO, —OH, —SO ₃ H, —PO ₃ H ₂ and quaternary ammonium and their salts by subjecting the pigment to physical treatment or chemical treatment. Or an active species having these dispersibility-imparting groups is bonded (grafted) to the surface of the pigment. Examples of physical treatment include vacuum plasma treatment. Examples of the chemical treatment include a wet oxidation method in which the pigment surface is oxidized with an oxidizing agent in water, a method in which a carboxyl group is bonded via a phenyl group by bonding p-aminobenzoic acid to the pigment surface, and the like. it can.

  In the present embodiment, a self-dispersing pigment that is surface-treated by an oxidation treatment with hypohalous acid and / or hypohalite or an oxidation treatment with ozone is preferable in terms of high color development.

  Moreover, as a self-dispersion type pigment, it is also possible to use a commercial item, such as Microjet CW-1 (trade name; manufactured by Orient Chemical Industries), CAB-O-JET200, CAB-O-JET250C, CAB-O. -JET260M, CAB-O-JET270Y, CAB-O-JET300 (trade name; manufactured by Cabot Corporation) and the like can be exemplified.

  The self-dispersing pigment may have a volume average particle diameter of 50 to 250 nm from the viewpoint that the dispersion stability in the ink composition, the OD value of the recorded image is higher, and the glossiness can be further improved. preferable. In addition, these volume average particle diameters can be obtained by particle size measurement using a Microtrac UPA150 (manufactured by Microtrac) or a particle size distribution analyzer LPA3100 (manufactured by Otsuka Electronics Co., Ltd.).

[Water-soluble organic solvent]
The ink composition contains a water-soluble organic solvent from the viewpoint of ensuring the printing quality of the ink jet printer and the reliability of ejection stability and prevention of nozzle clogging.

  Examples of the water-soluble organic solvent include glycerin, 1,2,6-hexanetriol, trimethylolpropane, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, pentaethylene glycol, dipropylene glycol, 2 -Butene-1,4-diol, 2-ethyl-1,3-hexanediol, 2-methyl-2,4-pentanediol, 1,2-octanediol, 1,2-hexanediol, 1,2-pentanediol Polyhydric alcohols such as 1,5-pentanediol and 4-methyl-1,2-pentanediol; alkyl alcohols having 1 to 4 carbon atoms such as ethanol, methanol, butanol, propanol, and isopropanol; ethylene glycol monomethyl Ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, ethylene glycol mono-iso-propyl ether, diethylene glycol mono-iso- Propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-t-butyl ether, diethylene glycol mono-t-butyl ether, triethylene glycol monobutyl ether, 1-methyl-1-methoxybutanol, propylene glycol monomethyl ether, propylene glycol monoethyl Ether, propire Glycol mono-t-butyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene Glycol ethers such as glycol mono-iso-propyl ether; 2-pyrrolidone, N-methyl-2-pyrrolidone; 1,3-dimethyl-2-imidazolidinone; formamide, acetamide; dimethyl sulfoxide; sorbitol, sorbitan; acetin, diacetin , Triacetin; sulfolane and the like, and one or more of these can be used.

  These water-soluble organic solvents are preferably contained in the ink composition in an amount of 10 to 90% by weight from the viewpoint of ensuring appropriate physical properties (such as viscosity) of the ink composition, printing quality, and reliability.

  In the present embodiment, preferably, the water-soluble organic solvent contains at least 15% by weight of (b) a polyhydric alcohol monoalkyl ether and / or a nitrogen-containing cyclic compound having a vapor pressure of 0.1 mmHg or less at 20 ° C., And (c) polyhydric alcohols. More preferably, for example, the ratio of the content of (a) water: (b) a polyhydric alcohol monoalkyl ether having a vapor pressure at 20 ° C. of 0.1 mmHg or less and / or a nitrogen-containing solvent: (c) a polyhydric alcohol. However, (a) :( b) :( c) = 1: 0.25-8: 0.1-7. Thereby, it is possible to provide an ink jet recording method having excellent reliability such as print quality, ejection stability, and clogging recovery. This is because polyhydric alcohols are suitable for controlling water retention (humidity) and penetrability of the ink composition into recording media such as plain paper, and polyhydric alcohol monoalkyl ethers and / or nitrogen-containing cyclic compounds are used. It is suitable for controlling the ejection stability and permeability of the ink composition to the recording medium. By using these in combination, the printing quality such as bleeding and unevenness is further secured, and further, the ejection stability, clogging recovery property, etc. A highly reliable ink-jet recording method can be provided.

  As the polyhydric alcohol monoalkyl ether having a vapor pressure at 20 ° C. of 0.1 mmHg or less, among the glycol ethers, for example, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoisobutyl ether, dipropylene glycol monomethyl ether, diethylene glycol Propylene glycol monoisopropyl ether, dipropylene glycol monoisopropyl ether, dipropylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monobutyl ether, tripropylene glycol monomethyl ether, tripropylene glycol monobutyl ether, etc. Examples of the cyclic compound include 1,3-dimethyl-2. -Imidazolidinone, 2-pyrrolidone, N-methyl-2-pyrrolidone and the like.

  As the polyhydric alcohols, any of the above polyhydric alcohols can be used, and in particular, 1,2-alkanes such as 1,2-pentanediol, 1,2-hexanediol, 1,2-octanediol and the like. It preferably contains a diol.

[Surfactant]
The ink composition contains a surfactant from the viewpoint of storage stability. As the surfactant, an anionic surfactant, a cationic surfactant, an amphoteric surfactant and a nonionic surfactant can be contained. A nonionic surfactant is particularly preferable from the viewpoint of obtaining an ink composition with less foaming and foaming.

  Further specific examples of nonionic surfactants include acetylene glycol surfactants, acetylene alcohol surfactants, polyoxyethylene nonyl phenyl ether, polyoxyethylene octyl phenyl ether, polyoxyethylene dodecyl phenyl ether, polyoxyethylene alkyl Ethers such as allyl ether, polyoxyethylene oleyl ether, polyoxyethylene lauryl ether, polyoxyethylene alkyl ether, polyoxyalkylene alkyl ether; polyoxyethylene oleic acid, polyoxyethylene oleic acid ester, polyoxyethylene distearic acid ester , Sorbitan laurate, sorbitan monostearate, sorbitan monooleate, sorbitan sesquioleate, polyoxy Esters such as ethylene monooleate and polyoxyethylene stearate; polyether-modified siloxane surfactants such as dimethylpolysiloxane; fluorine-containing surfactants such as fluorine alkyl esters and perfluoroalkyl carboxylates Can be mentioned. The nonionic surfactant can be used alone or in combination of two or more.

  Among the above nonionic surfactants, acetylene glycol surfactants and / or polyether-modified siloxane surfactants are particularly preferable in that they have little foaming and have excellent antifoaming performance.

  Further specific examples of the acetylene glycol surfactant include 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol. 3,5-dimethyl-1-hexyne-3ol, etc., but are also available commercially, for example, Surfynol 104, 82, 465, 485 manufactured by Air Products, manufactured by TG and Nisshin Chemical Co., Ltd. Olfin STG, Olfin E1010 and the like. Specific examples of the polyether-modified siloxane surfactant include BYK-345, BYK-346, BYK-347, BYK-348, UV3530, and the like manufactured by Big Chemie Japan. A plurality of these may be used in the ink composition, and the surface tension is preferably adjusted to 20 to 40 mN / m, and contained in the ink composition in an amount of 0.1 to 3.0% by weight.

[water]
The water contained in the ink composition is preferably pure water or ultrapure water such as ion exchange water, ultrafiltration water, reverse osmosis water, or distilled water. In particular, it is preferable to use water sterilized by ultraviolet irradiation or addition of hydrogen peroxide in order to prevent the generation of mold and bacteria and enable long-term storage of the ink composition.

[Resin emulsion]
The ink composition preferably contains a resin from the viewpoint of enhancing the dispersion stability of the pigment and securing the fixability to the recorded matter. In particular, it is preferable to use a resin emulsion from the viewpoint of the optical density (OD value) of plain paper and securing the fixability to a recorded matter.

  The resin emulsion is preferably a mixture of resin fine particles having a minimum film-forming temperature of 20 ° C. or higher and resin fine particles having a minimum film-forming temperature of less than 20 ° C. By using a mixture of resin fine particles having a minimum film-forming temperature of 20 ° C. or higher and resin fine particles having a minimum film-forming temperature of lower than 20 ° C. as a resin emulsion, the resin fine particles that form a film at 20 ° C. or higher are formed into a film at an ambient temperature. By improving the fixing property and abrasion resistance, the resin fine particles that form a film at less than 20 ° C. do not form a film at an ambient temperature, so that the particles remain on the paper and make the pigment particles more present on the paper surface. To achieve high color on plain paper and recycled paper.

  These resin emulsions are preferably one or more selected from the group consisting of acrylic resins, methacrylic resins, vinyl acetate resins, vinyl chloride resins, and styrene-acrylic resins. These resins may be used as a homopolymer or may be used as a copolymer, and any of a single phase structure and a multiphase structure (core-shell type) can be used.

  Furthermore, at least one of the two or more types of resin emulsions contained in the ink composition may be blended in the ink composition in the form of an emulsion of resin fine particles obtained by emulsion polymerization of unsaturated monomers. preferable. The reason for this is that even if the resin fine particles are added as they are to the ink composition, the dispersion of the resin fine particles may be insufficient, so that the emulsion form is preferable for the production of the ink composition. The emulsion is preferably an acrylic emulsion from the viewpoint of storage stability of the ink composition.

  An emulsion of resin fine particles (such as an acrylic emulsion) can be obtained by a known emulsion polymerization method. For example, it can be obtained by emulsion polymerization of an unsaturated monomer (such as an unsaturated vinyl monomer) in water containing a polymerization initiator and a surfactant.

  Examples of unsaturated monomers include acrylic acid ester monomers, methacrylic acid ester monomers, aromatic vinyl monomers, vinyl ester monomers, vinyl cyanide compounds generally used in emulsion polymerization. Examples include monomers, halogenated monomers, olefin monomers, and diene monomers. Furthermore, specific examples include methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl 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, glycidyl acrylate, etc .; methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n-amyl methacrylate, isoamyl Methacrylate, n-hexyl methacrylate, 2-ethyl Methacrylic esters such as hexyl methacrylate, octyl methacrylate, decyl methacrylate, dodecyl methacrylate, octadecyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, glycidyl methacrylate; and vinyl esters such as vinyl acetate; vinyl such as acrylonitrile and methacrylonitrile Cyanides; halogenated monomers such as vinylidene chloride and vinyl chloride; simple aromatic vinyl such as styrene, α-methylstyrene, vinyltoluene, 4-t-butylstyrene, chlorostyrene, vinylanisole, vinylnaphthalene Olefins such as ethylene and propylene; dienes such as butadiene and chloroprene; vinyl ether, vinyl ketone, vinyl pyrrolide Vinyl monomers such as ethylene; unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, fumaric acid and maleic acid; acrylamides such as acrylamide, methacrylamide and N, N′-dimethylacrylamide; 2-hydroxy Examples thereof include hydroxyl group-containing monomers such as ethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate and 2-hydroxypropyl methacrylate, and these can be used alone or in combination of two or more.

  A crosslinkable monomer having two or more polymerizable double bonds can also be used. Examples of the crosslinkable monomer having two or more polymerizable double bonds include polyethylene glycol diacrylate, triethylene glycol diacrylate, 1,3-butylene glycol diacrylate, 1,4-butylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, 1,9-nonanediol diacrylate, polypropylene glycol diacrylate, 2,2′-bis (4-acryloxypropyloxyphenyl) propane, 2,2 ′ -Diacrylate compounds such as bis (4-acryloxydiethoxyphenyl) propane; Triacrylate compounds such as trimethylolpropane triacrylate, trimethylolethane triacrylate, tetramethylolmethane triacrylate Tetraacrylate compounds such as ditrimethylol tetraacrylate, tetramethylolmethane tetraacrylate, pentaerythritol tetraacrylate; hexaacrylate compounds such as dipentaerythritol hexaacrylate; ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, triethylene glycol dimethacrylate, polyethylene glycol di Methacrylate, 1,3-butylene glycol dimethacrylate, 1,4-butylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, dipropylene glycol dimethacrylate, polypropylene glycol dimethacrylate, polybutylene glycol dimethacrylate Methacrylate, 2, Dimethacrylate compounds such as 2'-bis (4-methacryloxydiethoxyphenyl) propane; trimethacrylate compounds such as trimethylolpropane trimethacrylate and trimethylolethane trimethacrylate; methylenebisacrylamide; divinylbenzene and the like. It can be used alone or in combination.

  In addition to the polymerization initiator and surfactant used in emulsion polymerization, a chain transfer agent, further a neutralizing agent, and the like may be used according to a conventional method. In particular, ammonia and inorganic alkali hydroxides such as sodium hydroxide and potassium hydroxide are preferred as the neutralizing agent.

  In the present embodiment, the resin emulsion is 1 to 10 from the viewpoint of more effectively obtaining the ink jet proper physical property value, reliability (clogging, ejection stability, etc.), high OD value, fixing property, glossiness, etc. of the ink composition. It is preferably contained in the ink composition in the range of% by weight.

  On the other hand, the volume average particle diameter of the resin emulsion used in the ink composition is 20 from the viewpoint that the dispersion stability in the ink composition, the OD value of the recorded image is higher, and the glossiness can be further improved. It is preferable that it is -200 nm.

[Other additives]
A pH adjuster can be added to the ink composition. As the pH adjuster, alkali hydroxides such as lithium hydroxide, potassium hydroxide and sodium hydroxide and / or alkanolamines such as ammonia, triethanolamine, tripropanolamine, diethanolamine and monoethanolamine can be used. . In particular, it is preferably adjusted to pH 6 to 10 including at least one pH adjusting agent selected from alkali metal hydroxide, ammonia, triethanolamine, and tripropanolamine. If the pH is within this range, the clogging recoverability can be maintained without causing deterioration of the materials constituting the ink jet printer.

  If necessary, collidine, imidazole, phosphoric acid, 3- (N-morpholino) propanesulfonic acid, tris (hydroxymethyl) aminomethane, boric acid and the like can be used as a pH buffering agent.

  Trialkanolamines can also be suitably used as gloss imparting agents for ink compositions, and in order to form uniform gloss images on glossy recording media, yellow, magenta and cyan ink compositions Can be added to the product.

  The content of trialkanolamine used as the gloss imparting agent of the ink composition is 10 to 50% by weight with respect to 100% by weight of the pigment from the viewpoint of erosion to members used in the printer, ink viscosity and gloss. It is preferably 12 to 45% by weight, more preferably 1% by weight or more based on the total amount of the ink composition, and more preferably the upper limit is 3% by weight. Is 1% by weight.

  The trialkanolamine is not particularly limited, but triethanolamine and / or tripropanolamine are preferable from the viewpoint of improving printing stability and glossiness.

  Furthermore, an antifoaming agent, an antioxidant, an ultraviolet absorber, an antiseptic / antifungal agent, and the like can be added to each ink composition as necessary.

  Antioxidants and ultraviolet absorbers include allophanates such as allophanate and methyl allophanate, biurets such as biuret, dimethylbiuret and tetramethylbiuret, L-ascorbic acid and its salts, etc. Tinuvin 328, 900 manufactured by Ciba Geigy 1130, 384, 292, 123, 144, 622, 770, 292, Irgacor 252, 153, Irganox 1010, 1076, 1035, MD1024, or the like, or a lanthanide oxide or the like is used.

  Examples of antiseptic and fungicides include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, 1,2-dibenzisothiazolin-3-one (Avecia) Proxel CRL, Proxel BDN, Proxel GXL, Proxel XL-2, Proxel TN) and the like.

  The ink composition used in the present embodiment can be prepared in the same manner as the conventional ink composition using a conventionally known apparatus such as a ball mill, a sand mill, an attritor, a basket mill, a roll mill, or the like. In the preparation, it is preferable to remove coarse particles from the viewpoint of preventing nozzle clogging. The coarse particles are removed by, for example, filtering the ink obtained by mixing each component using a filter such as a membrane filter or a mesh filter, and removing particles of preferably 10 μm or more, more preferably 5 μm or more. Is called.

  In the present embodiment, the “inkjet recording method” means a method in which an ink composition is ejected as droplets from a fine nozzle by an inkjet recording apparatus, and the droplets are attached to a recording medium. This will be specifically described below.

  As a first method, there is an electrostatic suction method, which applies a strong electric field between the nozzle and the acceleration electrode placed in front of the nozzle, and continuously ejects ink from the nozzle in the form of droplets. This is a method in which a print information signal is applied to the deflection electrode while the ink droplet is flying between the deflection electrodes for recording, or a method in which the ink droplet is ejected in response to the print information signal without being deflected.

  The second method is a method in which ink droplets are forcibly ejected by applying pressure to the ink liquid with a small pump and mechanically vibrating the nozzle with a crystal resonator or the like. The ejected ink droplet is charged simultaneously with the ejection, and a printing information signal is given to the deflection electrode and recorded while the ink droplet flies between the deflection electrodes.

  The third method is a method using a piezoelectric element, in which a pressure and a print information signal are simultaneously applied to an ink liquid by a piezoelectric element to eject and record ink droplets.

  The fourth method is a method in which the ink liquid is rapidly expanded in volume by the action of heat energy, and the ink liquid is heated and foamed with a microelectrode in accordance with a print information signal to eject and record ink droplets.

  Any of the above methods can be used in the ink jet recording method using the ink composition of the present embodiment.

  According to the ink jet recording method of the present embodiment, by using the above-described ink composition, the ink jet recording apparatus that has been conventionally used can be used as it is without providing additional equipment, and the ink can be used as a recording medium. Cockling and curling can be prevented even when coated paper for printing with low absorbency is used.

[Recordings]
The recorded matter of this embodiment is recorded on a recording medium using at least the above-described inkjet recording method. By using the above-described ink jet recording method, the recorded matter can be used as it is without providing additional equipment in the conventionally used ink jet recording apparatus, and the recording medium can be plain paper or ink-absorbing. Cockling and curling can be prevented even when a low printing coated paper or the like is used.
[Example A]

1. Preparation of pigment dispersion M1 Organic pigment C.I. I. Pigment Red 122 65 g, Johncril 611 (Johnson Polymer Co., Ltd., average molecular weight 8100, acid value 53 KOH mg / g) 35 g, potassium hydroxide 1.70 g as a styrene-acrylic acid-based dispersion resin having a carboxylic acid group as an anionic group Then, 250 g of ultrapure water purified by an ion exchange method and a reverse osmosis method was mixed and dispersed for 10 hours by a ball mill using zirconia beads. The obtained dispersion liquid was filtered through a membrane filter (manufactured by Nippon Millipore Limited) having a pore size of about 8 μm to remove coarse particles, and further concentrated to obtain a pigment dispersion M1 having a pigment concentration of 50% by weight.

2. Preparation of Resin Emulsion A mixture of resin fine particles having a minimum film-forming temperature (hereinafter referred to as “MFT”) of less than 20 ° C. and resin fine particles of 20 ° C. or higher was prepared as a resin emulsion.

  Resin fine particles having an MFT of less than 20 ° C. were produced by polymerizing 600 g of methyl methacrylate, 125 g of butyl acrylate, 30 g of methacrylic acid, and 5 g of triethylene glycol diacrylate with 20 g of acrylamide. It was confirmed that the obtained resin fine particles did not form a film under a temperature condition of 20 ° C.

  Resin fine particles having an MFT of 20 ° C. or higher were produced by polymerizing 20 g of acrylamide with 130 g of styrene, 780 g of 2-ethylhexyl acrylate, 30 g of methacrylic acid, and 2 g of ethylene glycol dimethacrylate. It was confirmed that the obtained resin fine particles formed into a film under a temperature condition of 20 ° C.

3. Preparation of Ink Composition An ink composition containing the pigment dispersion M1, a water-soluble organic solvent, a resin emulsion, a surfactant, and water was prepared using the combinations shown in Table 1. The ink composition was prepared by mixing each component at the blending ratio shown in Table 1, stirring the mixture for 2 hours, and then filtering the mixture with a stainless steel filter having a pore diameter of about 5 μm. In addition, the numerical value shown in Table 1 is expressed as weight%.

4). Evaluation Test (1) Printing Method Using the ink composition (ink Nos. 1 to 3) shown in Table 1, using an inkjet printer PX-A550 (manufactured by Seiko Epson), magenta under the printing conditions shown in Table 2 below. A patch pattern of 100% duty of color was created. As recording media, OK top coat N (made by Oji Paper Co., Ltd.), which is a type of printing paper (coated paper for printing), and Xerox 4200 (made by Xerox), which is a type of plain paper, were used. Then, each evaluation test described later was performed using the patch pattern as a sample.

(2) Evaluation of optical density (OD value) The OD value of the patch portion was measured using a Gretag densitometer (manufactured by Gretag Macbeth). And the average value for every sample was calculated | required and the optical density value (OD value) was evaluated by the following evaluation criteria about the calculated average OD value. The results are shown in Table 3.
A: 1.2 or more B: 1.0 or more and less than 0.9 C: Less than 0.9

(3) Evaluation of cockling The unevenness (cockling) of each sample was measured using a laser displacement meter (LK-010, manufactured by Keyence Corporation). And the average value for every sample was calculated | required and the cockling was evaluated on the following evaluation criteria based on the calculated average value. The results are shown in Table 3.
A: Unevenness is less than 1.0 mm B: Unevenness is not less than 1.0 mm and less than 2.0 mm C: Unevenness is not less than 2.0 mm

(4) Fixability (dryness)
After printing, each sample was naturally dried day and night, and then the printed portion of the sample was rubbed with a finger to visually observe the state of the printed surface and the ink attached to the finger. The results were evaluated based on the following criteria. The results are shown in Table 3.
A: The printing surface does not change, and ink does not adhere to the finger. B: The ink on the printing surface slightly drops, but the ink does not adhere to the finger. C: The ink on the printing surface drops, and the ink adheres to the finger.

As is apparent from the results in Table 3, the ink jet recording method of this example was superior in optical density, print quality, and fixability as compared with the comparative example, and could suppress cockling and curling.
[Example B]

1. Preparation of Pigment Dispersion Solution 100 g of commercially available carbon black S170 (trade name, manufactured by Degussa) was mixed with 500 g of water and pulverized with a ball mill using zirconia beads. To this pulverized stock solution, 500 g of sodium hypochlorite (effective chlorine concentration: 12%) was dropped, and the mixture was boiled for 10 hours with stirring to perform wet oxidation. The obtained dispersion stock solution was filtered through glass fiber filter paper GA-100 (trade name: manufactured by Advantech Toyo Co., Ltd.), and further washed with water. The obtained wet cake is re-dispersed in 5 kg of water, desalted and purified with a reverse osmosis membrane until the electric conductivity becomes 2 mS / cm, and further concentrated until the pigment concentration becomes 50% by weight to self-disperse pigment A self-dispersed pigment liquid B1 having a dispersed particle was obtained.

2. Preparation of Resin Emulsion The resin emulsion was synthesized using a flask equipped with a stirrer, a nitrogen introducing tube, a cooling tube, and two dropping funnels. In one of the two dropping funnels, an emulsion obtained by emulsifying a mixed solution having the composition shown in Table 4 with a homomixer was placed. In the other dropping funnel, 0.3 part of potassium persulfate as a catalyst was added. A solution dissolved in 5 parts of water was added. In the flask, 0.2 part of sodium lauryl sulfate was dissolved in 190 parts of water, and the atmosphere in the flask was changed to a nitrogen atmosphere. Next, the solution in the flask was heated to 70 ° C. with a warm bath, and the solution in the dropping funnel was dropped into the solution over 4 hours while stirring at 250 rpm, and the reaction was performed. After completion of dropping, the mixture was further stirred for 4 hours. The reaction solution was cooled and then neutralized in an aqueous sodium hydroxide solution to obtain polymer particles having a nonvolatile content of 30%.

  Table 4 shows the ratio (% by weight) of each monomer when the total amount of the resin emulsion is taken as the standard (100%). Table 4 also shows the measurement results of the average particle diameter of the polymer particles and the minimum film-forming temperature (hereinafter referred to as “MFT”). The average particle size of the polymer particles was measured using a Coulter Counter N4 (trade name, manufactured by Coulter).

3. Preparation of Ink Composition An ink composition containing a self-dispersing pigment liquid, a water-soluble organic solvent, a resin emulsion, a surfactant, and water was prepared using the combinations shown in Table 5. The ink composition was prepared by mixing the components at the blending ratios shown in Table 5, stirring the mixture for 2 hours, and filtering through a stainless steel filter having a pore size of about 5 μm. In addition, the numerical value shown in Table 5 is represented as weight%.

4). Evaluation Test (1) Printing Method Evaluation machine equipped with an ink jet recording head having the “nozzle density” and “printing density in the scanning direction” shown in Table 6 for the ink compositions (ink Nos. 1 to 6) shown in Table 5 Filled. A 100% duty patch pattern was created under the printing conditions shown in Table 7. As recording media, OK Top Coat N (manufactured by Oji Paper Co., Ltd .; hereinafter referred to as “Evaluation Media 1”), which is a type of coated paper for printing (printing paper), and Xerox 4200, a type of plain paper (Xerox) (Hereinafter referred to as “evaluation media 2”). Then, each evaluation test described later was performed using the patch pattern as a sample.

(2) Evaluation of optical density (OD value) The OD value of the patch portion was measured using a Gretag densitometer (manufactured by Gretag Macbeth). And the average value for every sample was calculated | required and the optical density value (OD value) was evaluated by the following evaluation criteria about the calculated average OD value. The results are shown in Table 8.
A: OD value is 1.3 or more B: OD value is 1.2 or more and less than 1.3 C: OD value is 1.0 or more and less than 1.2 D: OD value is 0.9 or more and less than 1.0 E: OD value is less than 0.9

(3) Evaluation of printing quality After printing, each sample was visually observed, and the printing quality for each sample was evaluated according to the following evaluation criteria. The results are shown in Table 8.
A: Coloring is good and there is no unevenness or bleeding. B: Although unevenness and bleeding are slightly occurring, there is no practical problem. C: Unevenness is conspicuous. Slight blurring occurs. D: Unevenness and bleeding are noticeable and impractical.

(4) Evaluation of cock ring The unevenness (cock ring) of each sample was measured using a laser displacement meter (LK-010, manufactured by Keyence Corporation). And the average value for every sample was calculated | required and the cockling was evaluated on the following evaluation criteria based on the calculated average value. The results are shown in Table 8.
A: Unevenness is less than 1.0 mm B: Unevenness is not less than 1.0 mm and less than 2.0 mm C: Unevenness is not less than 2.0 mm

(5) Fixability (dryness)
After printing, each sample was naturally dried day and night, and then the printed portion of the sample was rubbed with a finger to visually observe the state of the printed surface and the ink attached to the finger. The results were evaluated based on the following criteria. The results are shown in Table 8.
A: The printing surface does not change, and ink does not adhere to the finger. B: The ink on the printing surface slightly drops, but the ink does not adhere to the finger. C: The ink on the printing surface drops, and the ink adheres to the finger.

As is apparent from the results in Table 8, the ink jet recording method of this example was superior in optical density, print quality, and fixability as compared with the comparative example, and could suppress cockling and curling.
[Example C]

1. Synthesis of water-insoluble polymer 20 parts by weight of an organic solvent (methyl ethyl ketone), 0.03 part by weight of a polymerization chain transfer agent (2-mercaptoethanol), a polymerization initiator, and each monomer shown in Table 9 were sufficiently substituted with nitrogen gas. The reaction mixture was polymerized with stirring at 75 ° C., and 0.9 part by weight of 2,2′-azobis (2,4-dimethylvaleronitrile dissolved in 40 parts by weight of methyl ethyl ketone with respect to 100 parts by weight of the monomer component was added. In addition, the polymer solution was obtained by aging for 1 hour at 80 ° C. The numerical values shown in Table 9 mean the ratio (% by weight) of each monomer when the total amount of the monomer mixture is taken as the standard (100%). .

2. Preparation of Pigment Dispersion (1) Preparation of Yellow Pigment Dispersion Y1 7.5 parts by weight of the water-insoluble polymer shown in Table 9 was dissolved in 45 parts by weight of methyl ethyl ketone, and 20% aqueous sodium hydroxide solution (neutralizing agent) ) Is added to neutralize the salt-forming group, and C.I. I. 20 parts by weight of Pigment Yellow 74 was added and kneaded in a bead mill for 2 hours. After 120 parts by weight of ion-exchanged water was added to the kneaded product thus obtained and stirred, methyl ethyl ketone was removed at 60 ° C. under reduced pressure, and a part of the water was further removed to obtain a solid content concentration of 20%. A weight% pigment dispersion Y1 was obtained.

(2) Preparation of Magenta Pigment Dispersion M1 A water-insoluble polymer of Table 9 was dissolved in 45 parts by weight of methyl ethyl ketone instead of 7.5 parts by weight, and 20 parts by weight of C.I. I. In place of Pigment Yellow 74, 20 parts by weight of C.I. I. Except for using Pigment Violet 19, it was prepared in the same manner as Yellow Pigment Dispersion Y1, and Pigment Dispersion M1 having a solid content concentration of 20% by weight was obtained.

(3) Preparation of Cyan Pigment Dispersion C1 12.5 parts by weight of the water-insoluble polymer in Table 9 was used instead of 7.5 parts by weight, and 20 parts by weight of C.I. I. In place of Pigment Yellow 74, 12.5 parts by weight of C.I. I. A cyan pigment dispersion C1 having a solid concentration of 20% by weight was prepared in the same manner as in the yellow pigment dispersion except that CI Pigment Blue 15: 4 was used.

(4) Preparation of Black Pigment Dispersion Liquid K1 The water-insoluble polymer of Table 9 was used in an amount of 15 parts by weight instead of 7.5 parts by weight, and 20 parts by weight of C.I. I. Instead of Pigment Yellow 74, 25 parts by weight of C.I. I. A black pigment dispersion K1 having a solid concentration of 20% by weight was prepared in the same manner as in the yellow pigment dispersion except that Pigment Black 7 (carbon black) was used.

(5) Preparation of Cyan Pigment Dispersion C2 20 parts by weight of the water-insoluble polymer shown in Table 9 was dissolved in 90 parts by weight of methyl ethyl ketone, and a predetermined amount of 20% aqueous sodium hydroxide solution (neutralizing agent) was added to the salt. The product group is neutralized, and C.I. I. 40 parts by weight of Pigment Blue 15: 4 was added and kneaded in a bead mill for 2 hours. After adding 120 parts by weight of ion-exchanged water to the kneaded product thus obtained and stirring, methyl ethyl ketone was removed at 60 ° C. under reduced pressure, and this was further concentrated to obtain a pigment having a solid content concentration of 50% by weight. Dispersion C2 was obtained.

3. Preparation of Ink Composition Each pigment dispersion (Y1, M1, C1, K1, C2) prepared as described above, each solvent, and ultrapure water were mixed in the mixing ratio (% by weight) shown in Table 10 below. And stirred for 2 hours. Subsequently, the mixture was filtered using a membrane filter (trade name, manufactured by Nippon Millipore Limited) having a pore size of about 8 μm to prepare ink compositions (1 to 5). In addition, the numerical value shown in Table 10 is represented as weight%.

4). Evaluation Test (1) Printing Method Evaluation machine equipped with an ink jet recording head having the “nozzle density” and “printing density in the scanning direction” shown in Table 11 for the ink compositions (ink Nos. 1 to 5) shown in Table 10 Filled. Then, a 100% duty patch pattern was created under the printing conditions shown in Table 12. As recording media, OK Top Coat N (made by Oji Paper Co., Ltd., written as “Evaluation Media 1” in Table 13), which is a type of printing paper (coated paper for printing), and Xerox 4200, which is a type of plain paper. (Manufactured by Xerox Corporation, written as “Evaluation Media 2” in Table 13) was used. Then, each evaluation test described later was performed using the patch pattern as a sample.

(2) Evaluation of optical density (OD value) The OD value of the patch portion was measured using a Gretag densitometer (manufactured by Gretag Macbeth). And the average value for every sample was calculated | required and the optical density value (OD value) was evaluated by the following evaluation criteria about the calculated average OD value. The results are shown in Table 13.
A: OD value is 1.3 or more B: OD value is 1.2 or more and less than 1.3 C: OD value is 1.0 or more and less than 1.2 D: OD value is 0.9 or more and less than 1.0 E: OD value is less than 0.9

(3) Evaluation of printing quality After printing, each sample was visually observed, and the printing quality for each sample was evaluated according to the following evaluation criteria. The results are shown in Table 13.
A: Coloring is good and there is no unevenness or bleeding. B: Although unevenness and bleeding are slightly occurring, there is no practical problem. C: Unevenness is conspicuous. Slight blurring occurs. D: Unevenness and bleeding are noticeable and impractical.

(4) Evaluation of cock ring The unevenness (cock ring) of each sample was measured using a laser displacement meter (LK-010, manufactured by Keyence Corporation). And the average value for every sample was calculated | required and the cockling was evaluated on the following evaluation criteria based on the calculated average value. The results are shown in Table 13.
A: Unevenness is less than 1.0 mm B: Unevenness is not less than 1.0 mm and less than 2.0 mm C: Unevenness is not less than 2.0 mm

(5) Fixability (dryness)
After printing, each sample was naturally dried day and night, and then the printed portion of the sample was rubbed with a finger to visually observe the state of the printed surface and the ink attached to the finger. The results were evaluated based on the following criteria. The results are shown in Table 13.
A: The printing surface does not change, and ink does not adhere to the finger. B: The ink on the printing surface slightly drops, but the ink does not adhere to the finger. C: The ink on the printing surface drops, and the ink adheres to the finger.

  As is apparent from the results in Table 13, the ink jet recording method of this example was superior in optical density, print quality, and fixability as compared with the comparative example, and could suppress cockling and curling.

Claims (12)

In an inkjet recording method for forming an image by discharging droplets of an ink composition comprising at least a pigment, a water-soluble organic solvent, a surfactant, and water onto a recording medium.
As the recording medium, a plain paper or a recording medium having an absorption layer of a paper support in which the water absorption within 30 msec ^1/2 from the start of contact in the Bristow method is 30 ml / m ² or less is used.
The ink composition droplets are 15 ng or less per droplet,
The amount of moisture adhering to the recording medium is 10 mg / inch ² or less,
Inkjet recording method.   The inkjet recording method according to claim 1, wherein the droplets of the ink composition are ejected from an inkjet recording head having a nozzle density of one color of 360 dpi or more.   The ink jet recording method according to claim 1 or 2, wherein the water content of the ink composition is 10 to 60% by weight.   The water-soluble organic solvent contains at least 15% by weight of (b) a polyhydric alcohol monoalkyl ether and / or nitrogen-containing cyclic compound having a vapor pressure at 20 ° C. of 0.1 mmHg or less, and (c) a polyvalent The inkjet recording method according to any one of claims 1 to 3, comprising an alcohol.   (A) Water: (b) Polyhydric alcohol monoalkyl ether having a vapor pressure at 20 ° C. of 0.1 mmHg or less and / or nitrogen-containing solvent: (c) The ratio of the content of polyhydric alcohol is (a) The inkjet recording method according to claim 4, wherein: (b) :( c) = 1: 0.25 to 8: 0.1 to 7.   The inkjet recording method according to any one of claims 1 to 5, wherein the concentration of the pigment is 6% by weight or more in terms of solid content.   The inkjet recording method according to any one of claims 1 to 6, wherein the pigment is a pigment coated with a water-insoluble polymer.   The inkjet recording method according to claim 1, wherein the pigment is a self-dispersing pigment.   The inkjet recording method according to claim 1, wherein the surfactant is an acetylene glycol surfactant and / or a poly-modified siloxane surfactant.   The ink jet recording method according to claim 1, wherein the ink composition further contains a resin emulsion.   The inkjet recording according to any one of claims 1 to 10, wherein the resin emulsion is a mixture of resin fine particles having a minimum film-forming temperature of 20 ° C or higher and resin fine particles having a minimum film-forming temperature of less than 20 ° C. Method.   The recorded matter recorded by the inkjet recording method of any one of Claims 1-11.