JP2015014006A - Ink set and inkjet recording method using the ink set - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink set for inkjet recording, capable of obtaining recorded matters with superior color properties and improved permeation on plain paper.SOLUTION: An ink set used for an inkjet recording method, in which a reactive solution and a color ink composition are adhered to a recording medium to perform recording, contains a reactive solution containing a polyvalent metal salt, and a first color ink composition containing at least a coloring material, a sparingly water-soluble 1,2-alkanediol, a surfactant and water.

Description

Background of the Invention

FIELD OF THE INVENTION The present invention relates to an ink set, and more specifically, an ink set used in an ink jet recording method for performing recording by attaching two liquids of a reaction liquid and a colored ink composition to a recording medium, and the ink therefor The present invention relates to an ink jet recording method using a set.

BACKGROUND ART An ink jet recording system is a recording system that performs printing by causing a droplet of an ink composition to fly and adhere to a recording medium. In the ink jet recording method, not only printing using only a single color ink such as black but also three colors of ink yellow (Y), magenta (M) and cyan (C), or black (K) is added thereto. Various hues are expressed using an ink set composed of four colors. In addition to the above-described YMCK color inks, an ink set provided with inks such as orange and green has been proposed as an ink set that has better color reproducibility than these three-color or four-color ink sets.

  In addition, in the ink jet recording method, an ink jet recording method using a so-called two-liquid method using a combination of the above-described ink such as YMCK and a reaction liquid has also been proposed (for example, JP-A-9-207424). In the ink jet recording method using the two liquids, when the reaction liquid and the ink are brought into contact with each other on the recording medium, the reaction liquid destroys the aggregation state of the ink components such as pigments, and the ink components are aggregated to form the recording medium. It is said that a high-quality printed matter with a high color density and less bleeding and unevenness can be obtained because aggregates are formed on the surface. However, depending on the type of recording medium used, color development and bleeding may be insufficient.

  By the way, in the ink jet recording method as described above, water-based ink is generally used for plain paper. However, as a recording medium, a water-based ink for ink-jet recording capable of forming a good image even on a low-absorbing recording medium. Ink has been proposed. For example, in Japanese Patent Application Laid-Open No. 2007-277342, low water absorption of printing paper or the like is achieved by using an ink containing a poorly water-soluble 1,2-alkanediol such as 1,2-octanediol and a surfactant. It has been proposed that a recorded matter having excellent glossiness and color reproducibility can be obtained with respect to a recording medium having high properties.

JP-A-9-207424 JP 2007-277342 A

  The present inventors have now disclosed an ink composition containing a poorly water-soluble 1,2-alkanediol used in a low water-absorbing recording medium such as the above-mentioned printing paper and a reaction liquid containing a specific reactant. The present inventors have obtained the knowledge that by applying an ink set combined with the above to plain paper, a recorded matter having excellent color developability and improved bleeding can be obtained. The present invention is based on this finding.

  Accordingly, an object of the present invention is to provide an ink set for ink jet recording which can obtain a recorded matter which is excellent in color developability and improved in bleeding against plain paper.

  Another object of the present invention is to provide an ink jet recording method using the above ink set.

The ink set according to the present invention is an ink set used in an ink jet recording method for performing recording by attaching a reaction liquid and a colored ink composition to a recording medium,
A first colored ink composition comprising at least a reaction liquid comprising a polyvalent metal salt, a coloring material, a slightly water-soluble 1,2-alkanediol, a surfactant, and water;
Is included.

An ink jet recording method according to another aspect of the present invention is an ink jet recording method in which recording is performed on a recording medium using an ink set including a reaction liquid and first and second colored ink compositions.
The reaction solution comprises a polyvalent metal salt;
The first colored ink comprises at least a coloring material, a poorly water-soluble 1,2-alkanediol, a surfactant, and water;
The second colored ink comprises at least a coloring material and water;
When the recording medium is plain paper, recording is performed by attaching the reaction liquid and the first colored ink to the recording medium,
When the recording medium is a low water-absorbing recording medium, recording is performed by attaching the reaction liquid and the second ink to the recording medium.

  According to the ink set of the present invention, it contains at least a reaction liquid containing a polyvalent metal salt, a coloring material, a slightly water-soluble 1,2-alkanediol, a surfactant, and water. By applying an ink set using the first colored ink composition as described above to plain paper, a recorded matter having excellent color development and improved bleeding can be obtained.

  Further, according to the ink jet recording method of the present invention, a reaction liquid containing a polyvalent metal salt, a coloring material, a poorly water-soluble 1,2-alkanediol, and a surfactant with respect to plain paper And a reaction liquid comprising a polyvalent metal salt with respect to a low water-absorbing recording medium such as printing paper, by applying an ink set using at least a first colored ink composition comprising at least water By applying an ink set comprising a coloring ink composition containing at least a coloring material and water and not containing a poorly water-soluble 1,2-alkanediol, plain paper and low water absorption recording For any of the media, it is possible to obtain a recorded matter having excellent color developability and improved bleeding.

When using plain paper as a recording medium, a graph showing the colorimetric values (D _c) of cyan in each monochromatic duty. When using the printing paper as a recording medium, a graph showing the colorimetric values (D _c) of cyan in each monochromatic duty. Graph showing the mean value in the case of using a plain paper as the recording medium, secondary color (green) of cyan in the duty colorimetric value (D _c) and yellow colorimetric value (D _y). Graph showing the mean value in the case of using the printing paper as a recording medium, secondary color (green) of cyan in the duty colorimetric value (D _c) and yellow colorimetric value (D _y).

Detailed description of the invention

<Definition>
In the present specification, “low-absorbing recording medium” means a recording medium whose recording surface has a water absorption of 10 mL / m ² or less from the start of contact to 30 msec ^1/2 in the Bristow method. In addition, a recording medium that does not have a water-based ink receiving layer or has a poor water-based ink receiving layer is shown.

  In the present specification, the hydrocarbon group portion of alkanediol, dialkylene glycol, alkanetriol, and hydroxyalkoxyalkanediol may be either linear or branched.

  Water-soluble means that the solubility in water at 20 ° C. (the amount of solute with respect to 100 g of water) is 10.0 g or more, and poorly water-soluble means the solubility in water (100 g of water). It means that the amount of solute relative to 1.0 g is less than 1.0 g.

<Ink set>
The ink set according to the present invention includes a reaction liquid containing a polyvalent metal salt, a coloring material, a poorly water-soluble 1,2-alkanediol, a surfactant, and water. 1 is an ink set that is used in an inkjet recording method in which a reaction liquid and a colored ink composition are attached to a recording medium to perform recording.

  Excellent color developability even on plain paper by using an ink set that combines a coloring ink composition containing a poorly water-soluble 1,2-alkanediol and a reaction solution containing a polyvalent metal salt. In addition, a recorded matter with improved bleeding can be obtained. Conventionally, a coloring ink composition containing a poorly water-soluble 1,2-alkanediol and a surfactant is applied to a recording medium with low water absorption, such as printing paper, so that bleeding, glossiness, color reproducibility, etc. Although improvements have been made, it is unexpected that such a colored ink composition was applied to plain paper in combination with a reaction solution containing a polyvalent metal salt to improve color development and bleeding. Met. The reason for this is not clear, but is considered as follows. That is, when the coloring ink composition contains the poorly water-soluble 1,2-alkanediol, the reaction of the reaction liquid occurs when the reaction liquid containing the polyvalent metal salt comes into contact with the coloring ink composition on the recording medium. Property is promoted, the ink components aggregate instantly, and the colored ink composition thickens. Since this thickening occurs before the colored ink composition penetrates into the recording medium, the colored ink composition remains on the surface of the recording medium and does not penetrate into the recording medium. As a result, even with a recording medium having high ink permeability, such as plain paper, it is considered that a recorded matter with improved recording density and excellent color development can be obtained and bleeding can be improved. Hereinafter, the reaction liquid and the colored ink composition constituting the ink set of the present invention will be described.

<First colored ink composition>
The colored ink composition constituting the ink set according to the present invention contains a coloring material, a hardly water-soluble 1,2-alkanediol, a surfactant, and water as essential components. The slightly water-soluble 1,2-alkanediol is preferably an alkanediol having 7 or more carbon atoms, more preferably an alkanediol having 7 to 10 carbon atoms, such as 1,2-heptanediol, 1,2- Examples include octanediol, 5-methyl-1,2-hexanediol, 4-methyl-1,2-hexanediol, and 4,4-dimethyl-1,2-pentanediol. Among these, 1,2-octanediol is more preferable.

  In the present invention, in addition to the above-mentioned poorly water-soluble 1,2-alkanediol, from water-soluble 1,2-alkanediol, dialkylene glycol, water-soluble alkanetriol, saccharide, and hydroxyalkoxyalkanediol. It is preferable to further include one or more compounds selected from the group consisting of: By including these components, the ejection stability of the colored ink composition is also improved. The shorter the alkyl chain length of dialkylene glycol, water-soluble alkanetriol, and hydroxyalkoxyalkanediol, the better the ejection stability. The short alkyl chain length means, for example, an alkyl chain length of 7 or less.

  In the present invention, the water-soluble 1,2-alkanediol is preferably an alkanediol having 6 or less carbon atoms, such as 1,2-hexanediol, 1,2-pentanediol, 1,2-butanediol, 4 -Methyl-1,2-pentanediol, 3,3-dimethyl-1,2-butanediol and the like. Among these, a water-soluble alkanediol having a surface tension of 28 mN / m or less in the case of a 15% aqueous solution is more preferable. 1,2-hexanediol (surface tension: 26.7 mN / m), 4-methyl 1,2 -Pentanediol (surface tension: 25.4 mN / m) and 3,3-dimethyl-1,2-butanediol (surface tension: 26.1 mN / m) are particularly preferred. From the viewpoint of odor during printing, 1,2-hexanediol is preferred.

  The dialkylene glycol is preferably a dialkylene glycol having 2 to 4 carbon atoms, and examples thereof include diethylene glycol, dipropylene glycol, and dibutadiene glycol. Preferably, dipropylene glycol is used.

  Furthermore, examples of the water-soluble alkanetriol include 1,2,6-hexanetriol and 3-methyl-1,3,5-pentanetriol.

  Examples of the saccharide include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides), and polysaccharides or derivatives thereof. Among these, glucose, mannose, fructose, ribose, xylose, arabinose, galactose, glucitol, sorbitol, maltose, cellobiose, lactose, sucrose, trehalose, maltotriose, phyllanose, raffinose, and the like are preferable. Among these, raffinose is particularly preferable. By adding raffinose to the ink composition of the present invention, the intermittent recording characteristics are improved.

The polysaccharide means a saccharide in a broad sense and includes substances widely present in nature such as alginic acid, α-cyclodextrin, cellulose and the like. Examples of derivatives of these saccharides include reducing sugars of the saccharides described above (for example, sugar alcohol (general formula: HOCH ₂ (CHOH) _n CH ₂ OH (where n represents an integer of 2 to 5)), oxidized sugar (For example, aldonic acid, uronic acid, etc.), amino acids, thio sugars, etc. Among these, sugar alcohols are particularly preferable, and specific examples include maltitol, sorbitol, xylitol, etc. These saccharides are Commercially available products may be used. For example, HS20, HS30, HS500 (manufactured by Hayashibara Shoji Co., Ltd.) and oligo GGF (manufactured by Asahi Kasei Co., Ltd.) can be suitably used.

  Further, in the present invention, the hydroxyalkoxyalkanediol is not particularly limited as long as the effects of the present invention are exhibited, but preferably a terminal hydroxyalkoxy-1,2-alkanediol is mentioned, and more preferably 3- (2 -Hydroxyethoxy) -1,2-propanediol, 4- (2-hydroxyethoxy) -1,2-butanediol, and 5- (2-hydroxyethoxy) -1,2-pentanediol.

  Further, it is considered that dialkylene glycol, water-soluble alkanetriol, saccharide, and hydroxyalkoxyalkanediol also have a function as a solubilizing agent for poorly water-soluble alkanediol.

  In the present invention, the addition amount of 1,2-slightly water-soluble alkanediol is preferably 1 to 3% by mass, more preferably 1.5 to 2.5% by mass, based on the entire ink composition. By being in this range, even when the ink is applied to a recording medium having low ink absorption such as printing paper, printing spots can be suppressed and solubility in the ink can be further improved.

  The amount of the water-soluble 1,2-alkanediol added is preferably 0.5 to 6% by mass, more preferably 0.5 to 3% by mass, based on the entire ink composition. By being in this range, it is possible to further improve the solubility of the hardly water-soluble 1,2-alkanediol in the ink and to further reduce the initial viscosity of the ink.

  Furthermore, the addition amount of dialkylene glycol is preferably 2 to 12% by mass, and more preferably 3 to 6% by mass with respect to the entire ink composition.

  In the present invention, the addition amount of the water-soluble alkanetriol is preferably 2 to 12% by mass, more preferably 3 to 6% by mass with respect to the entire ink composition.

  Furthermore, the addition amount of saccharides is preferably 2 to 12% by mass, more preferably 3 to 6% by mass with respect to the entire ink composition. By being in this range, the solubility of the poorly water-soluble 1,2-alkanediol in the ink can be improved more effectively, and the initial viscosity of the ink can be further reduced.

  Further, the addition amount of the hydroxyalkoxyalkanediol is preferably 2 to 12% by mass, more preferably 3 to 6% by mass with respect to the whole ink composition.

  Further, the addition amount of one or more compounds selected from water-soluble alkanetriols, saccharides, and hydroxyalkoxyalkanediols is preferably 2 to 12% by mass, more preferably 3 to 6% by mass with respect to the entire ink composition. %.

  Further, the sum of the contents of the slightly water-soluble 1,2-alkanediol and the water-soluble 1,2-alkanediol is preferably 6% by mass or less based on the ink composition. By setting it within this range, not only plain paper but also a recording medium having low ink absorbency such as printing paper does not cause aggregation and excellent ejection stability.

  According to the present invention, the sum of the contents of dialkylene glycol and water-soluble alkanetriol is preferably 3 to 18% by mass, more preferably 4 to 8%, based on the entire ink composition. % By mass.

  According to the invention, the sum of the contents of dialkylene glycol and saccharide is preferably 3 to 18% by mass, more preferably 4 to 8% by mass, based on the entire ink composition. It is.

  According to the invention, the sum of the contents of dialkylene glycol and hydroxyalkoxyalkanediol is preferably 3 to 18% by mass, more preferably 4 to 4%, based on the entire ink composition. 8% by mass.

  According to the present invention, the sum of the contents of dialkylene glycol and one or more compounds selected from water-soluble alkanetriols, saccharides, and hydroxyalkoxyalkanediols is 3 for the entire ink composition. It is preferable to contain -18 mass%, More preferably, it is 4-8 mass%.

  According to the invention, the sum of the contents of the slightly water-soluble 1,2-alkanediol, dialkylene glycol, and water-soluble alkanetriol is 21% by mass or less based on the ink composition. It is preferable.

  Further, according to the present invention, the sum of the contents of the slightly water-soluble 1,2-alkanediol, dialkylene glycol, and the saccharide is preferably 21% by mass or less based on the ink composition. .

  According to the invention, the sum of the contents of the slightly water-soluble 1,2-alkanediol, dialkylene glycol, and hydroxyalkoxyalkanediol is 21% by mass or less based on the ink composition. It is preferable.

  In addition, according to the present invention, inclusion of a poorly water-soluble 1,2-alkanediol, dialkylene glycol, and one or more compounds selected from the water-soluble alkanetriol, saccharide, and hydroxyalkoxyalkanediol The sum of the amounts is preferably 21% by mass or less based on the ink composition.

  In the present invention, the first colored ink composition may further comprise an alkyl ether of a polyhydric alcohol in addition to the above components. By adding an alkyl ether of a polyhydric alcohol, it is possible to improve clogging recovery in the ink cap for capping the ink jet head. Here, the clogging in the ink cap means that the waste liquid staying in the cap is dried and solidified, and this clogs the fine holes of the ink absorbent such as the nonwoven fabric in the ink cap. By improving the clogging recovery in the ink cap, it is possible to prevent the cleaning success rate from being lowered and to improve the nozzle clogging recovery.

  The alkyl ether of the polyhydric alcohol is preferably alkylene glycol methyl ether, and examples thereof include propylene glycol monomethyl ether, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, dipropylene glycol monomethyl ether, triethylene glycol dimethyl ether, and triethylene glycol monomethyl ether. From the viewpoint of cohesiveness, monomethyl ether of alkylene glycol is more preferable, and from the viewpoint of flash point, methyl ether of triethylene glycol is preferable. From the viewpoint of environmental toxicity and ecotoxicity, triethylene glycol monomethyl ether is preferred.

  Further, when triethylene glycol monomethyl ether is contained, it is preferably contained in an amount of 0.5 to 9.0% by mass, more preferably 0.5 to 3.0% by mass, based on the entire ink composition.

  Further, when triethylene glycol monomethyl ether is included, the content ratio with the poorly water-soluble 1,2-alkanediol is preferably 3: 1 to 1: 6, and is 3: 1 to 1: 1. It is more preferable. By setting it within this range, it is possible to further improve clogging recovery in the ink cap for capping the inkjet head.

  In the present invention, the sum of the contents of triethylene glycol monomethyl ether and water-soluble 1,2-alkanediol is not particularly limited, but may be 9.0% by mass or less based on the ink composition. Preferably, it is 3.0 mass% or less. By setting it within this range, it is possible to further improve clogging recovery in the ink cap for capping the inkjet head.

  As the color material contained in the first colored ink composition used in the present invention, both dyes and pigments can be used, but pigments can be preferably used from the viewpoint of light resistance and water resistance.

  As the pigment, inorganic pigments and organic pigments can be used, and each can be used alone or in combination. As the inorganic pigment, for example, in addition to titanium oxide and iron oxide, carbon black produced by a known method such as a contact method, a furnace method, or a thermal method can be used. Examples of the organic pigment include azo pigments (including azo lakes, insoluble azo pigments, condensed azo pigments, chelate azo pigments), polycyclic pigments (for example, phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, Dioxazine pigments, thioindigo pigments, isoindolinone pigments, quinofullerone pigments, etc.), dye chelates (for example, basic dye-type chelates, acidic dye-type chelates), nitro pigments, nitroso pigments, aniline black, and the like can be used.

  Specific examples of the pigment are appropriately given according to the type (color) of the ink composition to be obtained. For example, as a pigment for a yellow ink composition, C.I. I. Pigment Yellow 1, 2, 3, 12, 14, 16, 17, 73, 74, 75, 83, 93, 95, 97, 98, 109, 110, 114, 128, 129, 138, 139, 147, 150, 151, 154, 155, 180, 185 and the like, and one or more of these are used. Of these, C.I. I. It is preferable to use one or more selected from the group consisting of CI Pigment Yellow 74, 110, 128, and 129. Examples of the pigment for the magenta ink composition include C.I. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 168, 184, 202, 209; I. Pigment violet 19 and the like, and one or more of these may be used. Of these, C.I. I. Pigment red 122, 202, 209, and C.I. I. One or more selected from the group consisting of CI Pigment Violet 19 is preferably used, and a solid solution thereof is more preferable. Examples of the pigment for the cyan ink composition include C.I. I. Pigment Blue 1, 2, 3, 15: 3, 15: 4, 15:34, 16, 22, 60; I. Bat Blue 4, 60 etc. are mentioned, and one or more of these are used. Of these, C.I. I. Pigment Blue 15: 3 and / or 15: 4 are preferably used, especially C.I. I. Pigment Blue 15: 3 is preferably used.

  Examples of the pigment for the black ink composition include lamp black (CI pigment black 6), acetylene black, furnace black (CI pigment black 7), and channel black (CI pigment black). 7), carbons such as carbon black (CI Pigment Black 7), inorganic pigments such as iron oxide pigments, and organic pigments such as aniline black (CI Pigment Black 1). In carbon black, carbon black is preferably used. Specifically, as carbon black, # 2650, # 2600, # 2300, # 2200, # 1000, # 980, # 970, # 966, # 960, # 950, # 900, # 850, MCF-88, # 55, # 52, # 47, # 45, # 45L, # 44, # 33, # 32, # 30 (Mitsubishi Chemical Corporation), SpecialBlaek 4A, 550, Printex95, 90, 85, 80, 75 45, 40 (above, manufactured by Degussa), Regal 660, RmogulL, monarch 1400, 1300, 1100, 800, 900 (above, manufactured by Cabot), Raven 7000, 5750, 5250, 3500, 3500, 2500 ULTRA, 2000, 1500, 1255 1200, 1190 ULTRA, 1170, 100ULTRA, Raven5000UIII (or more, Columbian Co., Ltd.), and the like.

  In the present invention, a so-called surface-treated pigment that is a pigment that can be dispersed and / or dissolved in an aqueous medium without a dispersant described later may be used. Here, “dispersed and / or dissolved in an aqueous medium without a dispersant” means that the dispersoid (pigment) is stably present at the minimum particle size that can be dispersed in an aqueous medium without using a dispersant. The state that is. The “dispersant” refers to an additive such as a surfactant or a polymer material that is generally used for dispersing pigment particles in an aqueous medium. The “minimum particle size that can be dispersed” refers to the minimum particle size of the dispersoid that does not decrease any further even if the dispersion time is increased.

  The surface-treated pigment is preferably formed by bonding a “hydrophilic functional group and / or salt thereof” (hereinafter referred to as a dispersibility-imparting group) to the pigment surface. The dispersibility-imparting group may be directly bonded to the pigment surface, or may be bonded via an alkyl group, an alkyl ether group, an aryl group, or the like. Examples of the dispersibility-imparting group include one or more selected from the group consisting of a carboxyl group, a carbonyl group, a hydroxyl group, a sulfone group, a phosphoric acid group, and a quaternary ammonium salt.

  The surface-treated pigment is produced, for example, by bonding (grafting) the dispersibility-imparting group or the active species having the dispersibility-imparting group to the surface of the pigment by subjecting the pigment to physical treatment or chemical treatment. The Examples of physical treatment include vacuum plasma treatment. The chemical treatment includes, for example, a method in which the pigment surface is oxidized with an oxidizing agent in water, and a carboxyl group or a sulfone group is directly bonded to the pigment surface, or p-amino-benzoic acid is bonded to the pigment surface. Thus, a method of bonding a carboxyl group through a phenyl group can be mentioned.

  The concentration of the pigment is not particularly limited because it may be adjusted to an appropriate pigment concentration (content) when the ink composition is prepared, but in the present invention, the solid content concentration of the pigment is 6% by mass or more. It is preferable that the content be 12% by mass or more. When ink droplets adhere on the recording medium, the ink spreads on the surface of the recording medium, but by increasing the pigment solid concentration to 6% by mass or more, the fluidity of the ink after the wetting and spreading remains early. Since the ink is lost, bleeding can be further suppressed even when printing is performed on a recording medium such as printing paper at a low resolution.

  When a pigment other than the above-described surface-treated pigment is used, the pigment kneaded with the dispersant described later has both the glossiness of the image, the prevention of bronzing, and the storage stability of the ink composition, and is further glossy. From the viewpoint of forming a color image having excellent properties.

  The ink composition according to the present invention may comprise at least one resin selected from a styrene-acrylic acid copolymer resin, a urethane resin, and a fluorene resin as a dispersant for dispersing the colorant. preferable. These copolymer resins are adsorbed on the pigment to improve dispersibility.

  Specific examples of the hydrophobic monomer in the copolymer resin include, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, iso-propyl acrylate, iso-propyl methacrylate, n- Butyl acrylate, n-butyl methacrylate, sec-butyl acrylate, sec-butyl methacrylate, tert-butyl acrylate, tert-butyl methacrylate, n-hexyl acrylate, n-hexyl methacrylate, n-octyl acrylate, n-octyl methacrylate, iso- Octyl acrylate, iso-octyl methacrylate, 2-ethylhexyl acrylate, 2-ethylhexyl methacrylate, Sil acrylate, decyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 2-dimethylaminoethyl acrylate, 2 -Dimethylaminoethyl methacrylate, 2-diethylaminoethyl acrylate, 2-diethylaminoethyl methacrylate, glycidyl acrylate, glycidyl methacrylate, allyl acrylate, allyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, phenyl acrylate, phenyl methacrylate, nonyl phenyl acrylate, noni Phenyl methacrylate, benzyl acrylate, benzyl methacrylate, dicyclopentenyl acrylate, dicyclopentenyl methacrylate, bornyl acrylate, bornyl methacrylate, 1,3-butanediol diacrylate, 1,3-butanediol dimethacrylate, 1,4-butane Diol diacrylate, 1,4-butanediol dimethacrylate, ethylene glycol diacrylate, ethylene glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, triethylene glycol diacrylate, triethylene glycol dimethacrylate, tetraethylene glycol diacrylate, tetra Ethylene glycol dimethacrylate, polyethylene glycol di Acrylate, polyethylene glycol dimethacrylate, neopentyl glycol diacrylate, 1,6-hexanediol diacrylate, 1,6-hexanediol dimethacrylate, dipropylene glycol diacrylate, dipropylene glycol dimethacrylate, trimethylolpropane triacrylate, trimethylol Mention may be made of methylolpropane trimethacrylate, glycerol acrylate, glycerol methacrylate, styrene, methylstyrene, vinyltoluene and the like. You may use these individually or in mixture of 2 or more types.

  Specific examples of the hydrophilic monomer include acrylic acid, methacrylic acid, maleic acid, itaconic acid and the like.

  From the standpoint that the copolymer resin of the hydrophobic monomer and the hydrophilic monomer can form a color image having both glossiness of the color image, prevention of bronzing, and storage stability of the ink composition and excellent glossiness. Styrene- (meth) acrylic acid copolymer resin, styrene-methylstyrene- (meth) acrylic acid copolymer resin, or styrene-maleic acid copolymer resin, (meth) acrylic acid- (meth) acrylic acid ester copolymer resin, Alternatively, it is preferably at least one of styrene- (meth) acrylic acid- (meth) acrylic acid ester copolymer resin.

  The copolymer resin may be a resin (styrene-acrylic acid resin) containing a polymer obtained by reacting styrene with acrylic acid or an ester of acrylic acid. Alternatively, the copolymer resin may be an acrylic acid-based water-soluble resin. Alternatively, a salt such as sodium, potassium, or ammonium may be used.

  The content of the copolymer resin is 100 parts by mass of the pigment from the viewpoint of achieving a color image having excellent glossiness while being compatible with glossiness of the color image, prevention of bronzing, and storage stability of the ink composition. On the other hand, it is preferably 20 to 50 parts by mass, and more preferably 20 to 40 parts by mass.

  Further, in the present invention, by using a urethane resin as a pigment dispersant, a color image having both glossiness of a color image, prevention of bronzing, and storage stability of the ink composition and excellent glossiness can be formed. it can. The urethane resin is a resin containing a polymer obtained by reacting a diisocyanate compound and a diol compound, but in the present invention, it is a resin having a urethane bond and / or an amide bond and an acidic group. Is preferred.

  Examples of the diisocyanate compound include aromatic aliphatic diisocyanate compounds such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate, aromatic diisocyanate compounds such as toluylene diisocyanate and phenylmethane diisocyanate, and modified products thereof. .

  Examples of the diol compound include polyethers such as polyethylene glycol and polypropylene glycol, polyesters such as polyethylene abido and polybutylene abates, and polycarbonates.

  The urethane resin preferably has a carboxyl group.

  In the present invention, a fluorene resin can also be used as the pigment dispersant.

  The mass ratio of the solid content of the pigment to the solid content other than the pigment (the former / the latter) achieves a color image that has both glossiness of the color image, prevention of bronzing, and storage stability of the ink composition, and excellent glossiness. From the viewpoint of forming an image, it is preferably 100/20 to 100/80.

  The content of the above-mentioned copolymer resin is 100 masses of the pigment from the viewpoint of achieving a color image having both glossiness of a color image, prevention of bronzing, and storage stability of the ink composition and excellent glossiness. Preferably it is 20-50 mass parts with respect to a part, More preferably, it is 20-40 mass parts.

  The content of the urethane resin is based on 100 parts by weight of the pigment from the viewpoint of achieving a color image having excellent glossiness, prevention of bronzing, and storage stability of the ink composition, and being capable of forming a color image having further excellent glossiness. The amount is preferably 10 to 40 parts by mass, and more preferably 10 to 35 parts by mass.

  The content of the fluorene-based resin is 100 parts by mass of the pigment from the viewpoint of achieving a color image having excellent glossiness, bronzing prevention, and storage stability of the ink composition, and capable of forming a color image having further excellent glossiness. On the other hand, it is preferably 20 to 100 parts by mass, and more preferably 20 to 80 parts by mass.

  The total amount of the copolymer resin and the urethane resin is used so as to be 90 parts by mass or less (more preferably 70 parts by mass or less) with respect to 100 parts by mass of the pigment. In addition, the ink composition is preferable because it can achieve both the storage stability of the ink composition and can form a color image having further excellent gloss.

  The acid value of the copolymer resin is preferably from 50 to 320 from the viewpoint of achieving color image glossiness, prevention of bronzing, and storage stability of the ink composition and forming a color image having further excellent glossiness. Yes, more preferably 100-250.

  The acid value of the urethane resin is preferably 10 to 300 from the viewpoint of achieving color image glossiness, prevention of bronzing, and storage stability of the ink composition and forming a color image with further excellent glossiness. More preferably, it is 20-100. The acid value is the mg amount of KOH required to neutralize 1 g of resin.

  The weight average molecular weight (Mw) of the copolymer resin is preferably from the viewpoint of achieving color image glossiness, prevention of bronzing, and storage stability of the ink composition, and forming a color image with further excellent glossiness. It is 2,000-30,000, More preferably, it is 2,000-20,000.

  The weight average molecular weight (Mw) before cross-linking of the urethane resin is compatible with the glossiness of the color image, the prevention of bronzing, and the storage stability of the ink composition and from the viewpoint of forming a color image having further excellent glossiness. Preferably it is 100-200,000, More preferably, it is 1000-50,000. Mw is measured by GPC (gel permeation chromatography), for example.

  The glass transition temperature (Tg; measured in accordance with JISK6900) of the copolymer resin is from the viewpoint that both color image glossiness, bronzing prevention, and storage stability of the ink composition are compatible, and a color image with further excellent glossiness can be formed. Is preferably 30 ° C. or higher, more preferably 50 to 130 ° C.

  The glass transition temperature (Tg; measured in accordance with JISK6900) of the urethane resin is from the viewpoint of achieving a color image that is more glossy while being compatible with glossiness of the color image, prevention of bronzing, and storage stability of the ink composition. , Preferably it is -50-200 degreeC, More preferably, it is -50-100 degreeC.

  The above-mentioned copolymer resin may be adsorbed to the pigment in the pigment dispersion or may be liberated, and achieves both color image glossiness, prevention of bronzing, and storage stability of the ink composition. In addition, from the viewpoint of forming a color image having further excellent gloss, the copolymer resin preferably has a maximum particle size of 0.3 μm or less, and an average particle size of 0.2 μm or less (more preferably 0.1 μm or less). ) Is more preferable. The average particle diameter is an average value of the dispersion diameter (cumulative 50% diameter) as the particles actually formed in the dispersion liquid. For example, Microtrac UPA (Microtrac Inc.) is used. Can be measured.

The fluorene resin is not limited as long as it has a fluorene skeleton, and can be obtained, for example, by copolymerizing the following monomer units.
Cyclohexane, 5-isocyanate-1- (isocyanatomethyl) -1,3,3-trimethyl (CAS No. 4098-71-9)
Ethanol, 2,2 ′-[9H-fluorene-9-ylidenebis (4,1-phenyleneoxy)] bis (CAS No. 117344-32-8)
Propionic acid, 3-hydroxy-2- (hydroxymethyl) -2-methyl (CAS No. 4767-03-7)
Ethanamine, N, N-diethyl- (CAS No. 121-44-8)

  A surfactant may be used as the dispersant. Such surfactants include fatty acid salts, higher alkyl dicarboxylates, higher alcohol sulfates, higher alkyl sulfonates, condensates of higher fatty acids and amino acids, sulfosuccinate esters, naphthenates, liquid fats. Anionic surfactants such as oil sulfate esters and alkyl allyl sulfonates; Cationic surfactants such as fatty acid amine salts, quaternary ammonium salts, sulfonium salts and phosphoniums; polyoxyethylene alkyl ethers and polyoxyethylene alkyls Nonionic surfactants such as esters, sorbitan alkyl esters, polyoxyethylene sorbitan alkyl esters and the like can be mentioned. It goes without saying that the surfactant also functions as a surfactant when added to the ink composition.

  The first colored ink composition used in the present invention contains a surfactant as an essential component in addition to the above-mentioned poorly water-soluble 1,2-alkanediol. By applying a colored ink composition containing a poorly water-soluble 1,2-alkanediol and a surfactant to plain paper in combination with a reaction solution described later, color developability and bleeding are improved.

  As the surfactant used in the present invention, a polyorganosiloxane-based surfactant can be preferably used, and when forming a recorded image, the wettability to the surface of the recording medium can be improved to increase the ink permeability. it can. When a polyorganosiloxane-based surfactant is used, the above components are contained, so that the solubility of the surfactant in the ink is improved and the generation of insoluble matter can be suppressed, so that the ink has better ejection stability. A composition can be realized.

  Commercially available surfactants such as those described above may be used. For example, Olfine PD-501, Olfine PD-502, Olfine PD-570 (all manufactured by Nissin Chemical Industry Co., Ltd.) BYK-347. , BYK-348 (both manufactured by Big Chemie Co., Ltd.) and the like can be used.

（式中、Ｒは水素原子またはメチル基を表し、ａは２〜１１の整数を表し、ｍは２〜５０の整数を表し、ｎは１〜５の整数を表す。）で表される一種または二種以上の化合物を含んでなるか、または、上記式（Ｉ）の化合物において、Ｒが水素原子またはメチル基であり、ａが２〜１３の整数であり、ｍは２〜５０の整数であり、ｎは１〜５の整数である一種または二種以上の化合物を含んでなることがより好ましい。また、上記式（Ｉ）の化合物において、Ｒが水素原子またはメチル基であり、ａが２〜１３の整数であり、ｍは２〜５０の整数であり、ｎは１〜８の整数である一種または二種以上の化合物を含んでなることがより好ましい。あるいは、上記式（Ｉ）の化合物において、Ｒがメチル基であり、ａが６〜１８の整数、であり、ｍが０であり、ｎが１である一種または二種以上の化合物を含んでなることがより好ましい。このような特定のポリオルガノシロキサン系界面活性剤を使用することにより、インクの凝集むらがより改善される。 Further, as the polyorganosiloxane surfactant, the following formula (I):

(Wherein R represents a hydrogen atom or a methyl group, a represents an integer of 2 to 11, m represents an integer of 2 to 50, and n represents an integer of 1 to 5). Or in the compound of the above formula (I), R is a hydrogen atom or a methyl group, a is an integer of 2 to 13, and m is an integer of 2 to 50 More preferably, n comprises one or more compounds that are integers of 1 to 5. In the compound of the above formula (I), R is a hydrogen atom or a methyl group, a is an integer of 2 to 13, m is an integer of 2 to 50, and n is an integer of 1 to 8. More preferably, it comprises one or more compounds. Or in the compound of the said formula (I), R is a methyl group, a is an integer of 6-18, m is 0, n contains 1 type or 2 or more types of compounds. More preferably. By using such a specific polyorganosiloxane surfactant, the uneven aggregation of the ink is further improved.

  In the compound of the above formula (I), a is an integer of 2 to 5, m is an integer of 20 to 40, n is an integer of 2 to 4, and a is an integer of 7 to 11. M is an integer of 30 to 50, n is an integer of 3 to 5, a is an integer of 9 to 13, m is an integer of 2 to 4, and n is an integer of 1 to 2 It is more preferable to use a certain compound or a compound in which a is an integer of 6 to 10, m is an integer of 10 to 20, and n is an integer of 4 to 8. By using such a compound, the unevenness of ink aggregation can be further improved.

  In the compound of the above formula (I), R is a hydrogen atom, a is an integer of 2 to 5, m is an integer of 20 to 40, and n is an integer of 2 to 4, Alternatively, it is more preferable to use a compound in which a is an integer of 7 to 11, m is an integer of 30 to 50, and n is an integer of 3 to 5. By using such a compound, it is possible to further improve the uneven aggregation and bleeding of the ink.

  In the compound of the above formula (I), R is a methyl group, a is an integer of 9 to 13, m is an integer of 2 to 4, and n is an integer of 1 to 2, Alternatively, it is more preferable to use a compound in which a is an integer of 6 to 10, m is an integer of 10 to 20, and n is an integer of 4 to 8. By using such a compound, it is possible to further improve the uneven aggregation and bleeding of the ink.

  Furthermore, in the compound of the above formula (I), it is more preferable to use a compound in which R is a methyl group, a is an integer of 6 to 12, m is 0, and n is 1. By using such a compound, it is possible to further improve the uneven aggregation and bleeding of the ink.

  Moreover, in the compound of the said formula (I), R is a hydrogen atom, a is an integer of 7-11, m is an integer of 30-50, n is an integer of 3-5, , R is a methyl group, a is an integer of 9 to 13, m is an integer of 2 to 4, n is an integer of 1 to 2, R is a methyl group, and a is 6 It is most preferable to use a mixture of a compound having an integer of 10 to 10, m being an integer of 10 to 20, and n being an integer of 4 to 8. By using such a compound, it is possible to further improve the uneven aggregation and bleeding of the ink.

  The surfactant is preferably contained in the ink composition according to the present invention in an amount of 0.01 to 1.0% by mass, more preferably 0.05 to 0.50% by mass.

  In addition, the surfactant used in the present invention may include a gemini surfactant. By using a gemini surfactant in combination with the above components, the poorly water-soluble solvent can be uniformly dispersed, and as a result, the initial viscosity of the ink can be reduced. Therefore, it is possible to increase the amount of coloring material added to the ink composition and the amount of anti-clogging agent added, and as a result, not only plain paper but also the resin and particles for receiving ink are coated on the surface. Even with a recording medium having a porous surface, an image having excellent color developability can be realized. The “gemini-type surfactant” means a surfactant having a structure in which two surfactant molecules are bonded to each other via a linker.

（式中、Ｘ_１、Ｘ_２、およびＸ_３は、それぞれ独立して水素原子またはアルカリ金属を表すが、Ｘ_１、Ｘ_２、およびＸ_３の何れもが同時に水素原子またはアルカリ金属となることはなく、ＬおよびＭは、それぞれ独立して０または２を表すが、ＬおよびＭが同時に０または２となることはなく、ＮおよびＰは、それぞれ独立して０または２を表すが、ＮおよびＰが同時に０または２となることはなく、ＱおよびＲは、８〜１８の整数を表す）で表される界面活性剤を用いることが好ましい。 The gemini surfactant is a two-chain three-hydrophilic surfactant having a structure in which the hydrophilic group portions of a pair of one-chain surfactants are bonded to each other via a linker having a hydrophilic group. It is preferable. Moreover, it is preferable that the hydrophilic group part of said 1 chain type surfactant is an acidic amino acid residue, and it is preferable that the said linker is a basic amino acid. Specifically, a surfactant having a structure in which a pair of one-chain surfactants whose hydrophilic group portion is glutamic acid or aspartic acid is bonded via a linker such as arginine, lysine, or histidine. It is done. As the Gemini type surfactant as described above, in the present invention, the following formula (II):

(In the formula, X ₁ , X ₂ , and X ₃ each independently represent a hydrogen atom or an alkali metal, but all of X ₁ , X ₂ , and X ₃ are simultaneously a hydrogen atom or an alkali metal. L and M each independently represent 0 or 2, but L and M are not 0 or 2 at the same time, and N and P each independently represent 0 or 2, And P are not 0 or 2 at the same time, and Q and R are preferably a surfactant represented by the following formula:

  In the above formula (II), Na is preferred as the alkali metal, and Q and R are preferably about 10. Examples of such a compound include a sodium salt of a condensate of N-lauroyl-L-glutamic acid and L-lysine. As the compound represented by the above formula, a commercially available compound may be used. For example, Pericea is an aqueous solution containing 30% of a sodium salt of a condensate of N-lauroyl-L-glutamic acid and L-lysine. L-30 (Asahi Kasei Chemicals Co., Ltd.) etc. can be used conveniently.

  In the present invention, by using the above-mentioned Gemini type surfactant, it is possible to increase the wettability of the surface of the recording medium and improve the ink permeability when forming a recorded image. Since the solubility of the surfactant in the ink is improved and the generation of insoluble matters can be suppressed, an ink composition with more excellent ejection stability can be realized.

  Other surfactants, specifically, acetylene glycol surfactants, anionic surfactants, nonionic surfactants, amphoteric surfactants, and the like may be further added to the first colored ink composition.

  Among these, acetylene glycol surfactants include, for example, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6- Diol, or 3,5-dimethyl-1-hexyn-3ol, 2,4-dimethyl-5-hexyn-3-ol and the like can be mentioned. Commercially available acetylene glycol surfactants can also be used. For example, Olphine E1010, STG, Y (trade name, manufactured by Nissin Chemical Co., Ltd.), Surfynol 61, 104, 82, 465, 485 or TG (Trade name, manufactured by Air Products and Chemicals Inc.).

  The first colored ink composition preferably contains a penetrant in addition to the above components. As the penetrant, various surfactants such as an anionic surfactant, a cationic surfactant and an amphoteric surfactant, alcohols such as methanol, ethanol and iso-propyl alcohol, and glycol ethers can be suitably used. Specific examples of glycol ethers include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol mono-iso-propyl ether, ethylene glycol mono-n-butyl ether, ethylene glycol mono-iso-butyl ether, ethylene glycol mono-tert -Butyl ether, ethylene glycol monomethyl ether acetate, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-propyl ether, diethylene glycol mono-iso-propyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol mono-tert-butyl ether, triethylene Glycol mono-n-bu Ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol mono-n-propyl ether, propylene glycol mono-iso-propyl ether, propylene glycol mono-n-butyl ether, propylene glycol mono-tert-butyl ether, dipropylene glycol Monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol-iso-propyl ether, dipropylene glycol mono-n-butyl ether, dipropylene glycol mono-tert-butyl ether, 1-methyl -1-methoxybutanol and the like, and one or a mixture of two or more thereof It can be used.

  Among the above-mentioned glycol ethers, alkyl ethers of polyhydric alcohols are preferred, especially ethylene glycol monoethyl ether, ethylene glycol mono-n-butyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol mono-n-butyl ether, propylene. Glycol monomethyl ether, propylene glycol monoethyl ether, propylene glycol monobutyl ether, triethylene glycol monomethyl ether, triethylene glycol monoethyl ether, or triethylene glycol mono-n-butyl ether are preferred. More preferably, triethylene glycol mono-n-butyl ether is used. Needless to say, some of the alkyl ethers of the polyhydric alcohols also function as penetrants when added to the ink composition.

  In addition, glycol ethers as the penetrant may overlap with alkyl ethers of polyhydric alcohols used from the viewpoints of cohesiveness, flash point, and environmental toxicity and ecotoxicity. Some have both effects.

  The addition amount of the penetrant may be appropriately determined, but is preferably about 0.1 to 30% by mass, more preferably about 1 to 20% by mass.

  The first colored ink composition preferably comprises a recording medium solubilizer in addition to the above components. As the recording medium solubilizer, pyrrolidones such as N-methyl-2-pyrrolidone can be preferably used. The addition amount of the recording medium solubilizer may be appropriately determined, but is preferably about 0.1 to 30% by mass, more preferably about 1 to 20% by mass.

  The first colored ink composition may contain a wetting agent. It means a wetting agent used in a normal ink composition for ink jet recording. Specifically, glycerin, ethylene glycol, 1,3-propanediol, 3-methyl-1,3-butanediol, 1,3 -Water-soluble alkanediols having 3 to 5 carbon atoms such as butanediol and 1,2-pentanediol.

  The first colored ink composition contains the above-described coloring material, poorly water-soluble 1,2-alkanediol, and a surfactant as essential components, and other various additives, and also contains water as a solvent. To do. It is preferable to use pure water or ultrapure water such as ion exchange water, ultrafiltration water, reverse osmosis water, or distilled water. In particular, water obtained by sterilizing these waters by ultraviolet irradiation or addition of hydrogen peroxide is preferable because generation of mold and bacteria is prevented for a long period of time.

  The first colored ink composition may further contain a nozzle clogging preventive, antiseptic, antioxidant, conductivity adjusting agent, pH adjusting agent, viscosity adjusting agent, surface tension adjusting agent, oxygen absorber and the like. it can.

  Examples of preservatives and fungicides include sodium benzoate, sodium pentachlorophenol, sodium 2-pyridinethiol-1-oxide, sodium sorbate, sodium dehydroacetate, 1,2-dibenzthiazoline-3-one ( ICI's Proxel CRL, Proxel BND, Proxel GXL, Proxel XL-2, Proxel TN) and the like.

  Furthermore, as examples of pH adjusters, other solubilizers or antioxidants, amines such as diethanolamine, triethanolamine, propanolamine, morpholine and their modified products, potassium hydroxide, sodium hydroxide, hydroxide Inorganic salts such as lithium, ammonium hydroxide, quaternary ammonium hydroxide (tetramethylammonium, etc.), carbonates such as potassium carbonate, sodium carbonate, lithium carbonate, and other phosphates, or N-methyl-2-pyrrolidone, urea And L-ascorbic acid and salts thereof, such as ureas such as thiourea and tetramethylurea, allophanates such as allophanate and methylallohanate, and biurets such as biuret, dimethylbiuret and tetramethylbiuret.

  Further, the first colored ink composition may contain an antioxidant and an ultraviolet absorber. Examples thereof include Tinuvin 328, 900, 1130, 384, 292, 123, 144 of Ciba Specialty Chemicals. 622, 770, 292, Irgacor 252 153, Irganox 1010, 1076, 1035, MD1024, lanthanide oxide, and the like.

  The first colored ink composition can be produced by dispersing and mixing the above-described components by an appropriate method. Preferably, the pigment, polymer dispersant, and water are first used in a suitable dispersing machine (for example, ball mill, sand mill, attritor, roll mill, agitator mill, Henschel mixer, colloid mill, ultrasonic homogenizer, jet mill, ang mill, etc.). Mix to prepare a uniform pigment dispersion, then add separately prepared resin (resin emulsion), water, water-soluble organic solvent, sugar, pH adjuster, preservative, fungicide, etc. An ink solution is prepared. After sufficiently stirring, the target ink composition can be obtained by performing filtration in order to remove the coarse particle diameter and foreign matters that cause clogging. The filtration may be preferably performed using a glass fiber filter as a filter medium. The glass fiber is preferably a resin-impregnated glass fiber from the viewpoint of the electrostatic adsorption function. The pore diameter is preferably 1 to 40 microns, more preferably 1 to 10 microns, from the viewpoint of productivity and adsorption removal of charged free resin and the like. If the adsorption and removal of the charged free resin or the like is insufficient, the ejection stability may be significantly degraded. An example of the filter is Ultipore GF Plus manufactured by Nippon Pole.

<Second colored ink composition>
In addition to the first colored ink composition described above, the ink set according to the present invention may contain a second colored ink composition as the colored ink. The second colored ink composition contains at least a coloring material and water and does not contain the above-described poorly water-soluble 1,2-alkanediol. The second colored ink composition is applied to a low-water-absorbing recording medium such as printing paper in combination with a reaction liquid described later. Conventionally, as described above, an ink containing a poorly water-soluble 1,2-alkanediol such as 1,2-octanediol has been known as an ink composition suitable for a low water-absorbing recording medium. By recording on a low water-absorbing recording medium using such an ink, a recorded matter having excellent gloss and color reproducibility can be obtained. In the present invention, the ink composition that does not contain a poorly water-soluble 1,2-alkanediol and a reaction liquid containing a specific reactant are used in combination with a low water-absorbing recording medium, thereby providing excellent color developability. In addition, the present inventors have found that a recorded matter with improved bleeding can be obtained.

  The second colored ink composition contains a coloring material and water as essential components, but contains the same components as the first colored ink composition except that it does not contain a poorly water-soluble 1,2-alkanediol. In addition, components such as the alcohols, surfactants, penetrants, recording medium solubilizers, wetting agents and the like described above may be included. Further, the same coloring material and water as those of the first colored ink composition can be used.

<Reaction solution>
The ink set according to the present invention contains a reaction liquid in addition to the first and second colored ink compositions described above. The reaction solution used in the present invention basically contains at least a polyvalent metal salt. By applying the reaction liquid containing the polyvalent metal salt and the first colored ink composition described above to plain paper, it is possible to obtain a recorded matter having excellent color development and improved bleeding. Further, by applying a reaction liquid containing a polyvalent metal salt and the above-described second colored ink composition to a low water-absorbing recording medium, a recorded matter having excellent color development and improved bleeding is obtained. Can be obtained.

The polyvalent metal salt is composed of a divalent or higher polyvalent metal ion and an anion bonded to the polyvalent metal ion, and is soluble in water. Specific examples of polyvalent metal ions include divalent metal ions such as Ca ²⁺ , Cu ²⁺ , Ni ²⁺ , Mg ²⁺ , Zn ²⁺ , and Ba ²⁺ , Al ³⁺ , Fe ³⁺ , Cr ^And trivalent metal ions such as ³⁺ . Examples of the anion include Cl ⁻ , NO ₃ ⁻ , I ⁻ , Br ⁻ , ClO ₃ ⁻ , nitrate ion, and carboxylate ion.

  The carboxylate ion is preferably derived from a saturated aliphatic monocarboxylic acid having 1 to 6 carbon atoms or a carbocyclic monocarboxylic acid having 7 to 11 carbon atoms. Preferable examples of the saturated aliphatic monocarboxylic acid having 1 to 6 carbon atoms include formic acid, acetic acid, propionic acid, butyric acid, isobutyric acid, valeric acid, isovaleric acid, pivalic acid, hexanoic acid and the like. In particular, formic acid and acetic acid are preferred. The hydrogen atom on the saturated aliphatic hydrocarbon group of this monocarboxylic acid may be substituted with a hydroxyl group, and a preferred example of such a carboxylic acid is lactic acid. Moreover, as a preferable example of a C6-C10 carbocyclic monocarboxylic acid, benzoic acid, naphthoic acid, etc. are mentioned, More preferably, it is benzoic acid.

Among these polyvalent metal ions, a metal salt composed of Ca ²⁺ or Mg ²⁺ is preferable from the two viewpoints of the pH of the reaction solution and the quality of the obtained printed matter.

  The concentration of these polyvalent metal salts in the reaction solution may be appropriately determined as long as the recording quality and the effect of preventing clogging are obtained, but is preferably about 0.1 to 40% by mass, more preferably 5 to 5%. It is about 25% by mass.

  In the present invention, the reaction solution may contain a polyol in addition to the polyvalent metal salt. For example, glycerin, diethylene glycol, triethylene glycol, 1,5-pentanediol, 1,4-butanediol, sugar Etc. may be added. Examples of the sugar include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides), and polysaccharides. Glucose, mannose, fructose, ribose, xylose, arabinose, galactose, aldonic acid, glucosiyl, Examples include sorbit, maltose, cellobiose, lactose, sucrose, trehalose, maltotriose and the like.

  These polyols may be added alone or as a mixture of two or more. When added as a mixture of two or more, the addition amount is set to 1 or more by mass ratio with respect to the polyvalent metal salt as a total.

  In the present invention, the reaction liquid may contain a wetting agent as described above, and the inclusion of the wetting agent prevents the reaction liquid from drying and improves clogging of the head. The addition amount of the wetting agent is not particularly limited, but is preferably about 0.5 to 40% by mass, more preferably about 2 to 20% by mass.

  In the present invention, the reaction solution has a low boiling point such as methanol, ethanol, n-propyl alcohol, iso-propyl alcohol, n-butanol, sec-butanol, tert-butanol, iso-butanol, and n-pentanol. Organic solvents may be included, and the addition of these low-boiling organic solvents shortens the ink drying time. The addition amount of the low boiling point organic solvent is preferably 0.5 to 10% by mass, more preferably 1.5 to 6% by mass.

  Further, the reaction solution may contain the above-mentioned surfactant or penetrant, and may contain triethanolamine for pH adjustment. Furthermore, the reaction liquid may be colored by adding the coloring material described in the above-mentioned section of the ink composition, and may have the function of the ink composition.

<Inkjet recording method>
An ink jet recording method according to the present invention is an ink jet recording method in which recording is performed on a recording medium using an ink set including the above-described reaction liquid and first and second colored ink compositions. The first colored ink comprises at least a colorant, a poorly water-soluble 1,2-alkanediol, a surfactant, and water. When the colored ink of 2 comprises at least a coloring material and water and the recording medium is plain paper, the reaction liquid and the first colored ink are attached to the recording medium to perform recording, When the recording medium is a low water-absorbing recording medium, recording is performed by attaching the reaction liquid and the second ink to the recording medium.

  The recording method according to the present invention is carried out using an ink jet printer. As is well known, an ink jet printer is a printing apparatus that ejects ink droplets from a discharge port of a recording head (ink jet head) and attaches the ink droplets to a recording medium to form an image. There are two types of inkjet printers: a continuous type that forms an image by continuously ejecting ink from the nozzles of the recording head at predetermined time intervals and deflecting the ejected ink droplets, and an ink corresponding to the image data. However, in the present invention, an on-demand ink jet printer that can perform fine driving control and has a small amount of waste liquid is preferable. Further, the ink ejection method of the recording head includes an electro-mechanical conversion method using a piezoelectric element such as a piezo element and an electro-thermal conversion method using an electro-thermal conversion element such as a heater. Any inkjet printer equipped with a recording head can be used. In general, when an aqueous pigment ink is used, it is preferable to use an electro-mechanical conversion type recording head from the viewpoint of ejection stability.

  In the recording method according to the present invention, plain paper is used as a recording medium on which the reaction liquid and the first colored ink composition are adhered. Examples of usable plain paper include high-quality paper, recycled paper, copy paper, bond paper, paperboard, Japanese paper, and non-woven fabric. Ink acceptors mainly composed of porous particles such as silica, which have excellent ink absorbability. A known inkjet paper having a layer can also be used.

As a recording medium on which the reaction liquid and the second colored ink composition are attached, a low water-absorbing recording medium is used. As described above, the low water-absorbing recording medium is a recording medium whose recording surface has a water absorption of 10 mL / m ² or less from the start of contact to 30 msec ^1/2 in the Bristow method. This Bristow method is the most popular method for measuring the amount of liquid absorbed in a short time, and is also adopted by the Japan Paper Pulp Technology Association (JAPAN TAPPI). For details of the test method, refer to Standard No. of “JAPAN TAPPI Paper Pulp Test Method 2000”. 51 "Paper and paperboard-Liquid absorbency test method-Bristow method".

  Examples of the low water-absorbing recording medium include coated paper, and recording paper such as fine coated paper, art paper, coated paper, matte paper, and cast paper (these recording papers are also referred to as printing papers). Is mentioned.

  Coated paper is paper whose surface is coated with a paint to enhance aesthetics and smoothness. The paint can be prepared by mixing pigments such as talc, pyrophyllite, clay (kaolin), titanium oxide, magnesium carbonate, and calcium carbonate and an adhesive such as starch and polyvinyl alcohol. The paint is applied using a machine called a coater in the paper manufacturing process. There are two types of coater: an on-machine type in which papermaking and coating are performed as a single step by being directly connected to a paper machine, and an off-machine type in which the papermaking and coating are performed separately. It is mainly used for recording and is classified as coated paper for printing in the “Production Dynamic Statistics Classification” of the Ministry of Economy, Trade and Industry.

The finely coated paper refers to a recording paper having a coating amount of paint of 12 g / m ² or less. Art paper refers to recording paper obtained by applying a coating of about 40 g / m ^{2 to} high-grade recording paper (quality paper, paper with a chemical pulp usage rate of 100%). The coated paper refers to a recording paper coated with a paint of about 20 g / m ² to 40 g / m ² . The cast paper refers to a recording paper obtained by finishing art paper or coated paper by applying pressure to the surface with a machine called a cast drum so that the gloss and the recording effect are further enhanced.

  Printing paper is preferably used as the low water-absorbing recording medium, but art paper, high-quality paper used for POD (print on demand) applications, and dedicated paper for laser printers can also be used. For example, OKT + (manufactured by Oji Paper Co., Ltd.) is used as the main printing paper, Ricoh Business Coat Gloss 100 (manufactured by Ricoh Co., Ltd.) is used as the high-quality paper for POD, and LPCCTA4 (Seiko Epson Corporation) is used as the dedicated paper for the laser printer. Company-made).

The reaction liquid may be attached to the entire recording surface of the recording medium with a uniform adhesion amount, or may be selectively adhered only to a portion where ink is adhered. What is necessary is just to adjust suitably the adhesion amount of a reaction liquid in the range with which the predetermined effect is acquired, Preferably it is 0.05-5 g / m < ² > in conversion of solid content.

  In the present invention, the reaction liquid and the first or second colored ink composition may be provided so as to come into contact with each other on the recording surface of the recording medium. These may be applied on the recording surface of the recording medium, or the colored ink composition may be applied first.

  The time from applying one of the two liquids to be contacted to applying the other varies depending on the ejection amount, the type of the recording medium, and the like, but is preferably 5 ms to 60 seconds, and preferably 50 ms. More preferably, it is ˜500 ms. If this time lag is shorter than 5 ms, the other droplet may land on one of the droplets before the first applied droplet penetrates into the recording medium. The liquid may overflow on the recording medium and adversely affect image quality and drying properties. On the contrary, if the time lag exceeds 60 seconds, the first applied droplet completely penetrates into the inside of the recording medium and then the other droplet is ejected. Therefore, a predetermined image quality improvement effect is obtained. There is a risk of disappearing.

  EXAMPLES Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to these Examples.

<Preparation of ink composition and reaction solution>
Each component was mixed according to the composition of the following table and stirred for 2 hours. Then, yellow inks 1 and 2 and a reaction liquid were prepared by filtering through a membrane filter (trade name, manufactured by Nihon Millipore Limited) having a pore diameter of about 1.2 μm. The numerical values in the table below represent the content (% by mass) in the ink. Moreover, resin represents content (mass%) of solid content. In addition, the styrene-acrylic acid resin in the following table is a copolymer having a molecular weight of 1600 and an acid value of 150. In addition, fluorene-based resin is CAS No. It is a resin having a molecular weight of 3300, which contains a monomer having a fluorene skeleton represented by 117344-32-8 and a monomer composition ratio of about 50% by weight. The surfactant contained in the ink composition and the reaction liquid is a polyorganosiloxane surfactant, and in the above formula (I), R is a hydrogen atom, and a is an integer of 7 to 11. In which m is an integer of 30 to 50, n is an integer of 3 to 5, and in the above formula (I), R is a methyl group, a is an integer of 9 to 13, and m is It is a surfactant mixed with a compound that is an integer of 2 to 4 and n is an integer of 1 to 2.

  In the first ink (Y), C.I. I. In place of Pigment Yellow 74, C.I. I. A first ink (C) was obtained in the same manner as described above except that CI Pigment Blue 15: 3 was used. In the second ink (Y), C.I. I. In place of Pigment Yellow 74, C.I. I. A second ink (C) was obtained in the same manner as above except that CI Pigment Blue 15: 3 was used.

<Evaluation of recording quality>
Each ink and reaction liquid obtained above was used as an ink set, and assigned to the nozzle rows A to J of the ink cartridge of the inkjet printer (PX-H10000, manufactured by Seiko Epson Corporation) as follows.
Nozzle A: Reaction liquid Nozzle B: Reaction liquid Nozzle C: First ink (C)
Nozzle D: first ink (C)
Nozzle E: first ink (Y)
Nozzle F: first ink (Y)
Nozzle G: Second ink (C)
Nozzle H: Second ink (C)
Nozzle I: Second ink (Y)
Nozzle J: Second ink (Y)

Using the inkjet printer described above, solid paper (XeroxP) and printing paper (OKT +) are printed at 1440 x 720 dpi with a solid color duty of 0% to 100% and a secondary color duty of 0% to 200% to produce an evaluation sample. did.
In the recording with a single color, the following four types of droplets were discharged from each nozzle.
1. Nozzles A, B, C and D (combination of reaction liquid and first ink (C))
2. Nozzles A, B, G and H (combination of reaction liquid and second ink (C))
3. Nozzles C and D (first ink (C) only)
4). Nozzles G and H (second ink (C) only)
Further, in the recording with the secondary color, the following four types of droplets were discharged from each nozzle.
5. Nozzles A, B, C, D, E and F (combination of reaction liquid with first ink (C) and first ink (Y))
6). Nozzles A, B, G, H, I and J (combination of reaction liquid with second ink (C) and second ink (Y))
7). Nozzles C, D, E and F (first ink (C) and first ink (Y) only)
8). Nozzles G, H, I and J (second ink (C) and second ink (Y) only)

Next, the optical density (OD value) of the obtained evaluation sample was measured using a spectrocolorimeter (Spectrolino, manufactured by Macbeth Co.). The measurement conditions were as follows.
Light source: D50
Density filter: DIN 16536
UV cut filter: Existence White reference: Absolute value “Duty” is a value calculated by the following equation.
duty (%) = number of actual recording dots / (vertical resolution × horizontal resolution) × 100
(In the formula, “number of actual recording dots” is the number of actual recording dots per unit area, and “vertical resolution” and “horizontal resolution” are resolutions per unit area, respectively.)

When plain paper is used as a recording medium, the colorimetric values (D _c ) of cyan for each single-color duty have a relationship as shown in FIG. Further, when the printing paper is used as a recording medium, the colorimetric values (D _c ) of cyan at each single color duty have a relationship as shown in FIG.

When plain paper is used as the recording medium, the average value of cyan colorimetric values (D _c ) and yellow colorimetric values (D _y ) in the secondary color (green) duty is as shown in FIG. It was a great relationship. In addition, the average value of cyan colorimetric values (D _c ) and yellow colorimetric values (D _y ) in the secondary color (green) duty when printing paper is used as the recording medium is shown in FIG. It was such a relationship. 1 to 4, the dotted line portion in the graph represents a region in the evaluation sample where normal recording image quality cannot be ensured due to bleeding or uneven aggregation.

  As shown in FIGS. 1 and 3, when the recording medium is plain paper, a combination of an ink containing a poorly water-soluble 1,2-alkanediol and a surfactant and a reaction solution containing a polyvalent metal salt. The recorded matter printed using the other ink set can obtain a high-quality image without blurring or unevenness even when the duty is high, compared to the recorded matter printed using other ink sets. It can be seen that the optical density is also high. Further, as shown in FIGS. 2 and 3, when the recording medium is printing paper, a combination of an ink containing no poorly water-soluble 1,2-alkanediol and a reaction solution containing a polyvalent metal salt. The recorded matter printed using the ink set can obtain a high-quality image without blurring or unevenness even if the recorded matter is printed with another ink set, even if the duty is high. It can be seen that the optical density is also high.

Claims (8)

An ink set used in an ink jet recording method for recording by attaching a reaction liquid and a colored ink composition to a recording medium,
A first colored ink composition comprising at least a reaction liquid comprising a polyvalent metal salt, a coloring material, a slightly water-soluble 1,2-alkanediol, a surfactant, and water;
An ink set comprising:   The ink set according to claim 1, wherein the recording medium is plain paper.   The first colored ink composition is one or more compounds selected from the group consisting of water-soluble 1,2-alkanediol, dialkylene glycol, water-soluble alkanetriol, saccharide, and hydroxyalkoxyalkanediol. The ink set according to claim 1, further comprising:   The ink set according to any one of claims 1 to 3, wherein the surfactant is a polyorganosiloxane-based surfactant or a Gemini-type surfactant.   The ink set according to any one of claims 1 to 6, further comprising a second colored ink composition comprising at least a coloring material and water.   The first and / or second colored ink composition comprises at least one resin selected from the group consisting of styrene-acrylic acid copolymer resins, urethane resins, and fluorene resins. The ink set according to claim 5. An inkjet recording method for recording on a recording medium using an ink set comprising a reaction liquid and first and second colored ink compositions,
The reaction solution comprises a polyvalent metal salt;
The first colored ink comprises at least a coloring material, a poorly water-soluble 1,2-alkanediol, a surfactant, and water;
The second colored ink comprises at least a coloring material and water;
When the recording medium is plain paper, recording is performed by attaching the reaction liquid and the first colored ink to the recording medium,
An ink jet recording method in which recording is performed by attaching the reaction liquid and the second ink to a recording medium when the recording medium is a low-absorbing recording medium.   The method according to claim 1, wherein the first or second colored ink composition is attached to the recording medium before and / or after the reaction liquid is attached.

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