JP2011195613A - Ink set and inkjet recording method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink set which can improve the printing image quality in image recording by the inkjet system, particularly can inhibit the occurrence of bleeding in the formation of color images, and furthermore excels in fixing properties and an inkjet recording method.SOLUTION: The ink set includes a black ink and at least one color ink, the black ink includes either a polyurethane compound having a hydroxyl group in the molecule or a polyisocyanate compound, and the color ink includes the polyisocyanate compound or the polyurethane compound having a hydroxyl group which corresponds to either of these compounds.

Description

  The present invention relates to an ink set and an ink jet recording method which can improve the printing image quality in image recording by an ink jet method, particularly can suppress the occurrence of bleeding in the formation of a color image, and further have excellent fixability.

  Inkjet printers have been remarkably popular because of their low noise and low running cost, and color printers that can print on plain paper have become popular. However, all required color reproducibility, scratch resistance, durability, light resistance, image drying, character bleeding (feathering), color boundary bleeding (color bleed), double-sided printability, ejection stability, etc. It is very difficult to satisfy these characteristics, and the ink to be used is selected from the characteristics that are prioritized according to the application.

  Various approaches have been taken to improve the image quality of inkjet recorded images. Ink used for inkjet recording is mainly composed of water, and it contains a colorant and a wetting agent such as glycerin for the purpose of preventing clogging. When printing on fast paper, the ink penetrates into the inside and back of plain paper, so the image density and saturation are significantly lower than images output from offset printing, screen printing, and electrophotography. There was a drawback that the image looks poor.

In order to solve such problems, a recording medium in which a material for fixing a coloring material in ink when an image is formed on the surface of a recording medium such as plain paper is coated in advance, or a white pigment is applied on the surface. And recording media coated with water-soluble polymers have been proposed. For example, in Japanese Patent Application Laid-Open No. 2003-166183 of Patent Document 1, the ink receiving layer is composed of a resin layer obtained by crosslinking a polyurethane resin having a silanol group in a molecule with a crosslinking agent, and inkjet recording is performed on the ink receiving layer. After performing, the proposal which forms the overcoating layer which consists of a resin layer is made | formed.
However, such a method is expensive because it requires special processing, and thus is limited to special applications such as photographic image output, and has not been widely used.

  Therefore, in order to cope with a general recording medium such as plain paper, a pretreatment liquid having a color material cohesiveness is jetted or applied in advance on the recording medium, and ink is jetted onto the portion for printing. Ink jet recording methods that can increase image density and saturation even on plain paper have been proposed.

For example, Japanese Patent Application Laid-Open No. 2007-152149 of Patent Document 2 proposes a method in which reactive compounds that can react with each other in a printing layer are contained in colored ink and clear ink, respectively, and these are recorded by an inkjet printing method. Yes. However, such a recording method has a demerit that requires a mechanism for ejecting or applying a treatment liquid, a clear ink or the like in addition to the colored ink.
Further, in WO2006 / 129476 of Patent Document 3, a polymer compound having a plurality of side chains in a hydrophilic main chain and capable of crosslinking between side chains by irradiating active energy rays in the ink is disclosed. An ink-jet ink characterized by containing it has been proposed. However, even in such a method, a mechanism for irradiating active energy rays is required, and there is a demerit that the recording apparatus is large and expensive.

  While we have been studying such problems for many years, an ink combining a recording liquid containing a color material coated with a resin and a processing liquid containing fine particles having reactivity with the color material. A set has been previously proposed (see Japanese Patent No. 4001371 of Patent Document 4).

An object of the present invention is to solve the above-described problems and achieve the following objects.
That is, the present invention provides an ink set and an ink jet recording method that can improve the printing image quality in image recording by an ink jet method, particularly suppress the occurrence of bleeding in the formation of a color image, and further have excellent fixability. With the goal.

Means for solving the problems include the following. That is,
(1) "In an ink set comprising a black ink and at least one or more color inks, the black ink contains one of a polyurethane compound or a polyisocyanate compound having a hydroxyl group in the molecule, and the color ink An ink set comprising a polyisocyanate compound corresponding to any of these compounds or a polyurethane compound having a hydroxyl group in the molecule ",
(2) “The ink set according to item (1), wherein the polyurethane compound having a hydroxyl group is a self-emulsifying urethane resin emulsion”;
(3) "Ink set according to (1) or (2) above, wherein the polyurethane compound having a hydroxyl group is at least 0.1% by weight or more in the ink",
(4) "The ink set according to any one of (1) to (3) above, wherein the polyisocyanate compound is a water-dispersible isocyanate compound having a nonionic group",
(5) "The ink set according to any one of (1) to (4) above, wherein the color ink includes at least cyan ink, magenta ink, and yellow ink",
(6) “Black ink droplets containing either one of a polyurethane compound or a polyisocyanate compound having a hydroxyl group in the molecule in an ink set comprising a black ink and at least one or more color inks, and any of these compounds An ink jet recording method characterized by an increase in viscosity when color ink droplets containing a corresponding polyisocyanate compound or a polyurethane compound having a hydroxyl group in the molecule overlap in a liquid state.

  According to the present invention, the polyurethane compound having a hydroxyl group and the polyisocyanate compound cause cross-linking, and the colorant causes aggregation on the surface of the recording medium, so that the occurrence of bleeding can be suppressed and the image having excellent fixability. An ink set and an ink jet recording method can be provided.

FIG. 4 is a perspective explanatory view showing a state where an ink cartridge loading unit cover of the ink jet recording apparatus is opened. It is a schematic block diagram explaining the whole structure of an inkjet recording device. It is a schematic enlarged view which shows an example of the inkjet head of this invention. It is the schematic which shows an example of the ink bag of the ink cartridge of this invention. FIG. 5 is a schematic diagram illustrating an ink cartridge in which the ink bag of FIG. 4 is accommodated in a cartridge case.

  The polyurethane compound having a hydroxyl group and the polyisocyanate compound contained in the ink set are not particularly limited as long as they are a combination of components capable of crosslinking with each other. However, in many cases, energy such as heat and light is required for crosslinking, and in this case, it is necessary to select a recording medium having a very expensive and large apparatus and having heat resistance. Therefore, it is necessary to select a combination in which the crosslinking reaction proceeds as quickly as possible at room temperature.

In the water-based ink of the present invention, a combination of a self-emulsifying urethane resin emulsion and a water-dispersible isocyanate compound having a nonionic group is particularly preferable.
The following are mentioned as a polyurethane compound and a polyisocyanate compound.

[Polyurethane compound having a hydroxyl group in the molecule]
The polyurethane used in the present invention is obtained by polymerizing polyisocyanate, polyether polyol, polyester polyol, polylactone polyol, polycarbonate polyol, and the like.

  Examples of the polyether polyol include polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol, polyhexamethylene ether glycol and the like.

Examples of the polyester polyol include polyethylene adipate, polybutylene adipate, polyneopentyl adipate, poly-3-methylpentyl adipate, polyethylene / butylene adipate, polyneopentyl / hexyl adipate, and the like.
Examples of the polylactone polyol include polycaprolactone diol and polyomegahydroxycaproic acid polyol.

  Polycarbonate polyols include propanediol- (1,3), butanediol- (1,4), hexanediol- (1,6), diols such as diethylene glycol, triethylene glycol, and tetraethylene glycol, phosgene, and diphenyl. Known products are included such as products obtained from reaction with diaryl carbonates such as carbonates or cyclic carbonates such as ethylene carbonate and propylene carbonate.

Also suitable are polyester carbonates obtained from the polyesters or polylactones described above and phosgene, diaryl carbonates or cyclic carbonates.
Said resin emulsion expresses the further excellent water dispersibility by introduce | transducing an ionic group into resin. Examples of such ionic groups include sulfonic acid groups, carboxylic acid groups, sulfuric acid groups, phosphoric acid groups, phosphonic acid groups and phosphinic acid groups, or alkali metal bases, alkaline earth metal bases, ammonium bases, Examples include a primary to tertiary amine group. Among them, carboxylic acid alkali metal bases, carboxylic acid ammonium bases, sulfonic acid alkali metal bases and sulfonic acid ammonium bases are preferable, and sulfonic acid alkali metal bases and sulfonic acid ammonium bases are particularly preferable in terms of water dispersion stability. The introduction of the ionic group is performed by adding a monomer having an ionic group during the resin synthesis. Preferred as the salt are Li, K or Na salts.

The polyurethane compound is desirably contained at least 0.1% by weight or more in the ink. When the content is 0.1% by weight, it is possible to suppress the occurrence of bleeding in the improvement of the printing image quality in the image recording by the ink jet method, particularly in the formation of a color image, and it is possible to record an image with excellent fixability.
The polyisocyanate compound is preferably about 1/10 of the polyurethane compound content.

[Polyisocyanate compound]
Examples of the polyisocyanate in the present invention include aliphatic diisocyanate compounds such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, 1,4-cyclohexane diisocyanate, 4,4′- Alicyclic diisocyanate compounds such as dicyclohexylmethane diisocyanate, aromatic aliphatic diisocyanate compounds such as xylylene diisocyanate and tetramethylxylene diisocyanate, aromatic diisocyanate compounds such as toluylene diisocyanate and phenylmethane diisocyanate, and modified products of these diisocyanates (carbodiimide, uretdione) Ureitomine-containing metamorphs, etc.).

Examples of the urethane resin emulsion include Bondic series (manufactured by DIC), Takelac W, WS series (manufactured by Mitsui Chemicals Polyurethane), and the like.
Examples of the water-dispersible isocyanate compound include Bernock DNW series (manufactured by DIC), Takenate WD, and WB series (manufactured by Mitsui Chemicals Polyurethane).

[Other elements]
Next, elements other than those described above constituting the ink containing the colorant and the substantially colorless ink not containing the colorant will be described in carrying out the present invention.
-Colorant-
A pigment is used as the colorant in the present invention. Although there is no limitation in particular as a pigment, For example, the pigments listed below are used suitably. Moreover, you may use these pigments in mixture of multiple types.
Examples of organic pigments include azo, phthalocyanine, anthraquinone, quinacridone, dioxazine, indigo, thioindigo, perylene, isoindolenone, aniline black, azomethine, rhodamine B lake pigment, and carbon black. It is done.
Examples of inorganic pigments include iron oxide, titanium oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, bitumen, cadmium red, chrome yellow, and metal powder.
The carbon black used in the black pigment ink is carbon black produced by the furnace method and the channel method, the primary particle size is 15 to 40 millimicrons, the specific surface area by the BET method is 50 to 300 square meters / g, The DBP oil absorption is preferably 40 to 150 ml / 100 g, the volatile content is 0.5 to 10%, and the pH value is 2 to 9. As such a thing, for example, no. 2300, no. 900, MCF-88, no. 33, no. 40, no. 45, no. 52, MA7, MA8, MA100, no. 2200B (Mitsubishi Chemical), Raven700, 5750, 5250, 5000, 3500, 1255 (Columbia), Regal400R, 330R, 660R, MoguL, Monarch700, 800, 880, 900, 1000, 1100, 1300, Monarch1400 (Above, manufactured by Cabot), Color Black FW1, FW2, FW2V, FW18, FW200, S150, S160, S170, Printex 35, U, V, 140U, 140V, Special Black 6, 5, 4A, 4 (above, Degussa However, it is not limited to these.
Specific examples of color pigments are listed below.
Examples of pigments that can be used for yellow ink include C.I. I. Pigment Yellow 1 (Fast Yellow G), 2, 3, 12 (Disazo Yellow AAA), 13, 14, 16, 17, 20, 23, 24, 34, 35, 37, 42 (Yellow Iron Oxide), 53, 55 73, 74, 75, 81, 83 (disazo yellow HR), 86, 93, 95, 97, 98, 100, 101, 104, 108, 109, 110, 114, 117, 120, 125, 128, 129, 137, 138, 139, 147, 148, 150, 151, 153, 154, 155, 166, 168, 180, 185, and the like, but are not limited thereto.
Examples of pigments that can be used in magenta ink include C.I. I. Pigment Red 1, 2, 3, 5, 7, 9, 12, 17, 22 (Brilliant First Scarlet), 23, 31, 38, 48: 1 (Permanent Red 2B (Ba)), 48: 2 (Permanent Red 2B) (Ca)), 48: 3 (permanent red 2B (Sr)), 48: 4 (permanent red 2B (Mn)), 49: 1, 52: 2, 53: 1, 57: 1 (brilliant carmine 6B), 60: 1, 63: 1, 63: 2, 64: 1, 81 (Rhodamine 6G rake), 83, 88, 92, 97, 101 (Bengara), 104, 105, 106, 108 (Cadmium red), 112, 114, 122 (dimethylquinacridone), 123, 146, 149, 166, 168, 170, 172, 175, 176, 178, 179, 180 184, 185, 190, 192, 193, 202, 209, 215, 216, 217, 219, 220, 223, 226, 227, 228, 238, 240, 254, 255, 272, etc. It is not limited.
Examples of pigments that can be used for cyan ink include C.I. I. Pigment Blue 1, 2, 3, 15 (copper phthalocyanine blue R), 15: 1, 15: 2, 15: 3 (phthalocyanine blue G), 15: 4, 15: 6 (phthalocyanine blue E), 16, 17: 1, 2, 56, 60, 63, 64, bat blue 4, bat blue 60, and the like, but are not limited thereto.
For neutral colors, red, green and blue are C.I. I. Pigment red 177, 194, 224, C.I. I. Pigment orange 16, 36, 43, 51, 55, 59, 61, 71, C.I. I. Pigment violet 3, 19, 23, 29, 30, 37, 40, 50, C.I. I. Pigment green 7, 36, and the like.
Among these pigments, carbon black is preferable as the black pigment, carbon black produced by the furnace method and the channel method, the primary particles are 15 nm to 40 nm, and the specific surface area by the BET adsorption method is 50 m ² / g to 300 m ^2. / G, a DBP oil absorption of 4 ml / 100 g 0 to 150 ml / 100 g, a volatile content of 0.5 to 10% and a pH of 2 to 9 are used, and acidic carbon black having a pH of 6 or less is particularly preferred at a high concentration.
Examples of color pigments include C.I. I. Pigment Yellow 13, 17, 55, 74, 93, 97, 98, 110, 128, 139, 147, 150, 151, 154, 155, 180, 185; I. Pigment red 122, 202, 209; I. Pigment Blue 15: 3 and 15: 4 are particularly preferable.
There is no restriction | limiting in particular in the average particle diameter of the said pigment, According to the objective, it can select suitably, 10 nm-150 nm are preferable, 20 nm-100 nm are more preferable, 30 nm-80 nm are still more preferable. When the average particle diameter exceeds 150 nm, not only the saturation of the printed image is lowered, but also thickening aggregation during ink storage and clogging of the nozzle during printing are likely to occur. On the other hand, when the average particle diameter of the pigment is less than 10 nm, not only the light resistance is lowered but also the storage stability tends to be deteriorated.
The average particle diameter of the pigment is, for example, a micro-track UPA-150 manufactured by Nikkiso Co., Ltd., and a sample diluted with pure water so that the pigment concentration (mass concentration) in the measurement sample is 0.01% by mass. , Particle refractive index 1.51, particle density 1.4 g / cm ³ , solvent parameter means 50% average particle diameter (D50) measured at 23 ° C. using parameters of pure water.
The pigment concentration in the ink is preferably 2 to 15% by weight, more preferably 3 to 12% by weight, and still more preferably 4 to 10% by weight. If the pigment concentration is less than 2% by weight, the image strength tends to be inferior due to insufficient coloring power, and if it exceeds 15% by weight, not only the storage stability of the ink is lowered but also the image tends to be dull. .

-Dispersant-
The pigments listed above can be made into an inkjet recording liquid by dispersing them in an aqueous medium using a polymer dispersant or a surfactant. As a dispersant for dispersing such a pigment, a normal water-soluble resin or a water-soluble surfactant can be used.
Specific examples of water-soluble resins include styrene, styrene derivatives, vinyl naphthalene derivatives, aliphatic alcohol esters of α, β-ethylenically unsaturated carboxylic acids, acrylic acid, acrylic acid derivatives, maleic acid, maleic acid derivatives, itacon. Examples thereof include block copolymers consisting of at least two monomers selected from acids, itaconic acid derivatives, fumaric acid, fumaric acid derivatives, etc., random copolymers, or salts thereof. These water-soluble resins are alkali-soluble resins that are soluble in an aqueous solution in which a base is dissolved. Among them, a resin having a weight average molecular weight of 3000 to 20000 is used as a dispersion when used in an inkjet recording liquid. It is particularly preferred because of the advantages that it can be reduced in viscosity and can be easily dispersed.
The simultaneous use of the polymer dispersant and the self-dispersing pigment is a preferable combination because an appropriate dot diameter can be obtained. The reason is not clear, but it is thought as follows.
By containing the polymer dispersant, the penetration into the recording paper is suppressed. On the other hand, since the aggregation of the self-dispersing pigment is suppressed by containing the polymer dispersant, the self-dispersing pigment can smoothly spread in the lateral direction. Therefore, it is considered that the dots spread widely and thinly and ideal dots can be formed.

In addition, specific examples of the water-soluble surfactant that can be used as a dispersant in the present invention are generally classified into nonionic, anionic, and amphoteric, and are appropriately selected and used according to the pigment type or ink formulation.
Nonionic surfactants include polyoxyethylene lauryl ether, polyoxyethylene myristyl ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene alkyl ether such as polyoxyethylene oleyl ether, and polyoxyethylene octylphenyl ether. Polyoxyethylene alkylphenyl ethers such as polyoxyethylene nonylphenyl ether, polyoxyethylene-α-naphthyl ether, polyoxyethylene-β-naphthyl ether, polyoxyethylene monostyryl phenyl ether, polyoxyethylene distyryl phenyl ether, Polyoxyethylene alkyl naphthyl ether, polyoxyethylene monostyryl naphthyl ether, polyoxyethylene And distyryl naphthyl ether. In addition, surfactants such as polyoxyethylene polyoxypropylene block copolymers in which a part of polyoxyethylene of these surfactants is replaced with polyoxypropylene, and aromatic rings such as polyoxyethylene alkylphenyl ether A surfactant obtained by condensing a compound with formalin or the like can also be used.

  The nonionic surfactant has an HLB of preferably 12 to 19.5, more preferably 13 to 19. If the HLB is less than 12, there is a tendency for the dispersion stability to deteriorate due to poor conformity of the surfactant to the dispersion medium. If the HLB exceeds 19.5, the surfactant becomes difficult to adsorb to the pigment, so that the dispersion stability is also reduced. There is a tendency to deteriorate.

Anionic surfactants include polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl phenyl ether sulfate, polyoxyethylene monostyryl phenyl ether sulfate, polyoxyethylene distyryl phenyl ether sulfate, polyoxyethylene alkyl ether phosphorus Acid salt, polyoxyethylene alkyl phenyl ether phosphate, polyoxyethylene monostyryl phenyl ether phosphate, polyoxyethylene distyryl phenyl ether phosphate, polyoxyethylene alkyl ether carboxylate, polyoxyethylene alkyl phenyl ether Carboxylate, polyoxyethylene monostyryl phenyl ether carboxylate, polyoxyethylene distyryl phenyl ether carboxylate, naphthalene Phosphonate formalin condensate, melanin sulfonate formalin condensate, dialkyl sulfosuccinate ester salt, sulfosuccinic acid alkyl disalt, polyoxyethylene alkyl sulfosuccinic acid disalt, alkyl sulfoacetate, α-olefin sulphonate, alkylbenzene sulfone Acid salts, alkylnaphthalene sulfonates, alkyl sulfonates, N-acyl amino acid salts, acylated peptides, soaps and the like can be mentioned.
Further, the pigment can be provided with dispersibility by coating with a resin having a hydrophilic group and encapsulating the pigment.

As a method for coating a water-insoluble pigment with an organic polymer and microencapsulating, all conventionally known methods can be used. Conventionally known methods include chemical production methods, physical production methods, physicochemical methods, mechanical production methods, and the like. In particular,
Interfacial polymerization method (a method in which two types of monomers or two types of reactants are separately dissolved in a dispersed phase and a continuous phase, and both substances are reacted at the interface between them to form a wall film);
In-situ polymerization method (method of supplying a liquid or gas monomer and catalyst, or two reactive substances from either one of the continuous phase core particles to cause a reaction to form a wall film);
・ Liquid-cured coating method (method of forming a wall film by insolubilizing droplets of a polymer solution containing core material particles in a liquid with a curing agent);
-Coacervation (phase separation) method (a method in which a polymer dispersion in which core material particles are dispersed is separated into a coacervate (concentrated phase) and a dilute phase having a high polymer concentration to form a wall film);
・ Liquid drying method (preparing a liquid in which a core material is dispersed in a solution of a wall membrane material, placing the dispersion in a liquid in which the continuous phase of this dispersion is not miscible, and forming a composite emulsion to dissolve the wall membrane material. A method of forming a wall film by gradually removing the medium in the medium);
Melt dispersion cooling method (using a wall film material that melts into a liquid state when heated and solidifies at room temperature, this material is heated and liquefied, the core material particles are dispersed in it, cooled to fine particles, and cooled to the wall. A method of forming a film);
・ Air suspension coating method (Method of forming a wall membrane by suspending powder core material particles in the air with a fluidized bed and suspending them in an air stream while spraying and mixing the coating solution of the wall membrane material) ;
-Spray drying method (a method in which the encapsulated stock solution is sprayed and contacted with hot air to evaporate and dry the volatile components to form a wall film);
-Acid precipitation method (at least a part of anionic groups of organic polymer compounds containing anionic groups is neutralized with a basic compound to give solubility in water and kneaded in an aqueous medium with a colorant. Then, neutralize or acidify with an acidic compound, deposit organic compounds and fix them on the colorant, and then neutralize and disperse))
-Phase inversion emulsification method (a mixture containing an anionic organic polymer having dispersibility in water and a colorant is used as an organic solvent phase, and water is added to the organic solvent phase or And the like).

  Examples of organic polymers (resins) used as the material constituting the microcapsule wall membrane material include polyamide, polyurethane, polyester, polyurea, epoxy resin, polycarbonate, urea resin, melamine resin, phenol resin, and polysaccharide. , Gelatin, gum arabic, dextran, casein, protein, natural rubber, carboxypolymethylene, polyvinyl alcohol, polyvinylpyrrolidone, polyvinyl acetate, polyvinyl chloride, polyvinylidene chloride, cellulose, ethyl cellulose, methyl cellulose, nitrocellulose, hydroxyethyl cellulose, acetic acid Cellulose, polyethylene, polystyrene, (meth) acrylic acid polymer or copolymer, (meth) acrylic acid ester polymer or copolymer, (meth) acrylic acid (Meth) acrylic acid ester copolymer, styrene- (meth) acrylic acid copolymer, styrene-maleic acid copolymer, sodium alginate, fatty acid, paraffin, beeswax, water wax, hardened beef tallow, carnauba wax, albumin, etc. .

Among these, organic polymers having an anionic group such as a carboxylic acid group or a sulfonic acid group can be used. Nonionic organic polymers include, for example, polyvinyl alcohol, polyethylene glycol monomethacrylate, polypropylene glycol monomethacrylate, methoxypolyethylene glycol monomethacrylate or their (co) polymers, and 2-oxazoline cationic ring-opening polymers. Is mentioned. In particular, a completely saponified product of polyvinyl alcohol is particularly preferable because it has low water solubility and is easily dissolved in hot water but difficult to dissolve in cold water.
Further, the amount of the organic polymer constituting the wall membrane material of the microcapsule is 1% by weight or more and 20% by weight or less based on the water-insoluble colorant such as an organic pigment or carbon black. By setting the amount of the organic polymer within the above range, the content of the organic polymer in the capsule is relatively low so that the pigment develops due to the organic polymer covering the pigment surface. Can be suppressed. If the amount of the organic polymer is less than 1% by weight, it is difficult to exert the effect of encapsulation. Conversely, if the amount exceeds 20% by weight, the color developability of the pigment is significantly reduced. In consideration of other characteristics, the amount of the organic polymer is preferably in the range of 5 to 10% by weight based on the water-insoluble colorant.

That is, since a part of the color material is exposed without being substantially covered, it is possible to suppress a decrease in color developability, and conversely, a part of the color material is not substantially exposed without being exposed. Since it is coated, it is possible to simultaneously exhibit the effect that the pigment is coated. The number average molecular weight of the organic polymers used in the present invention is preferably 2000 or more from the viewpoint of capsule production. Here, “substantially exposed” means not the partial exposure associated with defects such as pinholes and cracks, but a state where it is intentionally exposed.
Furthermore, if an organic pigment or self-dispersing carbon black, which is a self-dispersing pigment, is used as a colorant, the dispersibility of the pigment is improved even if the content of the organic polymer in the capsule is relatively low. In addition, since sufficient storage stability of the ink can be secured, it is more preferable for the present invention.

  It is preferable to select an organic polymer suitable for the microencapsulation method. For example, in the case of interfacial polymerization, polyester, polyamide, polyurethane, polyvinyl pyrrolidone, epoxy resin and the like are suitable. In the case of using the in-situ polymerization method, a polymer or copolymer of (meth) acrylic acid ester, (meth) acrylic acid- (meth) acrylic acid ester copolymer, styrene- (meth) acrylic acid copolymer, Polyvinyl chloride, polyvinylidene chloride, polyamide and the like are suitable. In the case of the liquid curing method, sodium alginate, polyvinyl alcohol, gelatin, albumin, epoxy resin and the like are suitable. In the case of the coacervation method, gelatin, celluloses, casein and the like are suitable. In addition, in order to obtain a fine and uniform microencapsulated pigment, it is possible to use all conventionally known encapsulation methods other than those described above.

When the phase inversion method or the acid precipitation method is selected as the microencapsulation method, anionic organic polymers are used as the organic polymers constituting the wall membrane material of the microcapsules.
The phase inversion method is a composite or composite of an anionic organic polymer having self-dispersibility or solubility in water and a colorant such as a self-dispersible organic pigment or self-dispersible carbon black, or self A mixture of a colorant such as a dispersible organic pigment or self-dispersing carbon black, a curing agent, and an anionic organic polymer is used as an organic solvent phase, and water is added to the organic solvent phase, or the organic solvent is submerged in water. In this method, a solvent phase is introduced and microencapsulation is performed while self-dispersion (phase inversion emulsification) is performed. In the above phase inversion method, there is no problem even if the organic solvent phase is mixed with a recording liquid vehicle or additives. In particular, it is more preferable to mix a liquid medium of a recording liquid because a dispersion liquid for recording liquid can be directly produced.

  On the other hand, in the acid precipitation method, a part or all of the anionic group of the anionic group-containing organic polymer is neutralized with a basic compound, and a colorant such as a self-dispersing organic pigment or self-dispersing carbon black, A water-containing cake obtained by a production method comprising a step of kneading in an aqueous medium and a step of neutralizing and acidifying an acidic compound to precipitate an anionic group-containing organic polymer and fixing it to a pigment, This is a method of microencapsulation by neutralizing a part or all of an anionic group using a compound. By doing in this way, the aqueous dispersion containing the anionic microencapsulated pigment which is fine and contains many pigments can be manufactured.

  Examples of the solvent used for microencapsulation as described above include alkyl alcohols such as methanol, ethanol, propanol and butanol; aromatic hydrocarbons such as benzol, toluol and xylol; methyl acetate Esters such as ethyl acetate and butyl acetate; Chlorinated hydrocarbons such as chloroform and ethylene dichloride; Ketones such as acetone and methyl isobutyl ketone; Ethers such as tetrahydrofuran and dioxane; Cellosolves such as methyl cellosolve and butyl cellosolve Etc. The microcapsules prepared by the above method are once separated from these solvents by centrifugation or filtration, and then stirred and redispersed with water and the necessary solvent, and used for the intended present invention. A recording liquid that can be used is obtained. The average particle diameter of the encapsulated pigment obtained by the above method is preferably 50 nm to 180 nm.

-Penetration agent-
By adding a penetrant to the ink, the surface tension is reduced, and the penetration of the ink droplets onto the recording medium such as paper increases after the ink droplets have landed, thereby reducing feathering and color bleeding. it can. Surfactants are mainly used as penetrants, and are classified into nonionic, anionic and amphoteric depending on the polarity of the hydrophilic group. Further, it is classified into fluorine type, silicone type, acetylene type, etc. according to the structure of the hydrophobic group.
The appropriate surface tension range in the present invention is 20 to 35 mN / m.

Nonionic surfactants include, for example, polyols, glycol ethers, polyoxyethylene alkyl ethers, polyoxyethylene polyoxypropylene alkyl ethers, polyoxyethylene alkyl esters, polyoxyethylene sorbitan fatty acid esters, polyoxyethylene alkylphenyl ethers, Examples include polyoxyethylene alkylamine, polyoxyethylene alkylamide, acetylene glycol and the like.
Examples of the anionic surfactant include polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, laurate, polyoxyethylene alkyl ether sulfate, and the like.

  Fluorosurfactants include perfluoroalkyl sulfonates, perfluoroalkyl carboxylates, perfluoroalkyl phosphates, perfluoroalkyl ethylene oxide adducts, perfluoroalkyl betaines, perfluoroalkylamine oxide compounds, etc. Can be mentioned. Generally speaking, commercially available fluorine compounds include Surflon S-111, S-112, S-113, S121, S131, S132, S-141, S-144, S-145 (manufactured by Asahi Glass Co., Ltd.), Fullrad FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, FC-431, FC-4430 (manufactured by Sumitomo 3M), MegaFuck F-470, F -1405, F474 (manufactured by DIC), Zonyl FS-300, FSN, FSN-100, FSO, FSO-100 (manufactured by DuPont), F-top EF-351, 352, 801, 802 (manufactured by Gemco), FT -250, 251 (manufactured by Neos), PF-151N, PF-136A, PF-156A (manufactured by OMNOVA), etc. . Among these, FSO, FSO-100, FSN, FSN-100, and FS-300 manufactured by Dupont are preferable because they can provide good print quality and storage stability.

Examples of the silicone surfactant include polyether-modified silicone compounds.
Polyether-modified silicone compounds are side-chain type (pendant type) with a polyether group introduced into the side chain of polysiloxy acid, one-end type with a polyether group introduced into one end of polysiloxane, and both-end type introduced into both ends (ABA type), polysiloxane side-chain end-type with polysiloxane introduced on both side chain and both ends, polysiloxane (A) with polyether group introduced and unintroduced polysiloxane (B) repeated It can be classified into a bonded ABn type, a branched type in which a polyether group is introduced at the end of a branched polysiloxane, and the like. Although there is no particular limitation in the present invention, a side chain type (pendant type) having a structure in which a polyether group is introduced into the side chain of polysiloxane is preferred.

As commercially available products, KF-351A, KF-352A, KF-353, KF-354L, KF-355A, KF-615A, KF-945, KF-618, KF-6011, KF-6015, KF- 6004 (manufactured by Shin-Etsu Chemical Co., Ltd.), SF-3771, SF-8427, SF-8428, SH-3749, SH-8400, FZ-2101, FZ-2104, FZ-2118, FZ-2203, FZ-2207, L -7604 (manufactured by Dow Corning Toray), BYK-345, BYK-346, BYK-348 (manufactured by Big Chemie Japan), and the like.
As acetylene glycol surfactants, 2,4,7,9-tetramethyl-5-decyne-4,7-diol, 3,6-dimethyl-4-octyne-3,6-diol, 3,5 -Acetylene glycol type | system | groups, such as dimethyl- 1-hexyn-3-ol, etc. are mentioned.
For example, Surfynol 104, 82, 465, 485, TG (manufactured by Air Products) can be used.
When the surfactant is added as a penetrating agent to the ink, the addition amount is preferably 0.05 to 5% by weight, more preferably 0.1 to 3% by weight.
In the ink of the present invention, two or more surfactants may be used in combination. In order to improve the permeability, a polyol having 8 to 11 carbon atoms such as 2-ethyl-1,3-hexanediol and 2,2,4-trimethyl-1,3-pentanediol may be used in combination.

-Water-soluble organic solvent (wetting agent)-
The ink of the present invention uses water or a hydrophilic organic solvent as a liquid medium. For the purpose of preventing the ink from drying (as a wetting agent) and improving the dispersion stability, the water-soluble organic solvent is used. Contain. Examples of the water-soluble organic solvent include the following. A mixture of a plurality of these water-soluble organic solvents may be used.
Glycerin, diethylene glycol, 1,3-butanediol, 3-methyl-1,3-butanediol, triethylene glycol, propylene glycol, dipropylene glycol, trimethylolpropane, trimethylolethane, ethylene glycol, diethylene glycol, dipropylene glycol, Tripropylene glycol, tetraethylene glycol, hexylene glycol, polyethylene glycol, polypropylene glycol, 1,5-pentanediol, 1,6-hexanediol, glycerol, 1,2,6-hexanetriol, 1,2,4-butane Polyols such as triol, 1,2,3-butanetriol, petriol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether Polyhydric alcohol alkyl ethers such as diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether, and polyhydric alcohol aryls such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether Ethers, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam, γ-butyrolactone and other nitrogen-containing heterocyclic compounds, formamide Amides such as N-methylformamide, N, N-dimethylformamide, monoethanolamine, diethanolamine, trieta Amines such as allylamine, monoethylamine, diethylamine and triethylamine (in the case of using these amines, a combination with the urethane resin emulsion is desirable), sulfur-containing compounds such as dimethyl sulfoxide, sulfolane and thiodiethanol, propylene carbonate , Ethylene carbonate, γ-butyrolactone, and the like.

  In addition to the water-soluble organic solvent, other wetting agents may be used, and as such wetting agents, those containing sugar are preferable. Examples of saccharides include monosaccharides, disaccharides, oligosaccharides (including trisaccharides and tetrasaccharides) and polysaccharides, preferably glucose, mannose, fructose, ribose, xylose, arabinose, galactose, maltose, cellobiose, Examples include lactose, sucrose, trehalose, and maltotriose. Here, the polysaccharide means a saccharide in a broad sense, and is used to include a substance that exists widely in nature such as α-cyclodextrin and cellulose.

Examples of derivatives of these saccharides include reducing sugars of the saccharides described above (for example, sugar alcohol [general formula HOCH ₂ (CHOH) nCH ₂ OH (n = 2 to 5)), oxidized sugar (for example, aldonic acid). , Uronic acids, etc.), amino acids, thioic acids, etc. Sugar alcohols are particularly preferred, and specific examples include D-sorbitol, sorbitan, maltitol, erythritol, lactitol, xylitol and the like.

  In particular, in the present invention, when glycerin, 1,3-butanediol, or 3-methyl-1,3-butanediol is used, an ink having excellent storage stability and ejection stability can be produced.

  The ratio of pigment to wetting agent has a great influence on the ejection stability of ink from the head. If the pigment solid content ratio is high, but the amount of the wetting agent is small, water evaporation near the ink meniscus of the nozzle advances, resulting in ejection failure.

  The amount of the wetting agent is about 10 to 50% by weight of the whole ink. The ratio of the total weight of the colorant and the resin emulsion to the total weight of the wetting agent in the ink is preferably 0.5 to 12.5, more preferably 1.0 to 6.0, and most preferably 2.0 to 5.0. Range. Ink within this range has very good drying, storage and reliability tests.

-Resin emulsion-
The ink of the present invention is sufficiently fixed, but a resin emulsion may be added for the purpose of further improving image scratch resistance and storage stability when a pigment is used as a colorant. An emulsion of an acrylic resin, a styrene-acrylic resin, an acrylic silicone resin, or a fluororesin is preferable for improving image scratch resistance, and an emulsion of a urethane resin is particularly preferable for improving storage stability. However, since there are few resin emulsions that can simultaneously improve image scratch resistance and storage stability, two types of resin emulsions can be used in combination. These resin emulsions can be appropriately selected from commercially available ones as required.

  Examples of the resin emulsion include J-450, J-734, J-7600, J-352, J-390, J-7100, J-741, J74J, J-511, J-840, J-775, HRC-1645, HPD-71 (styrene-acrylic resin emulsion, both manufactured by Johnson Polymer), UVA383MA (acrylic-silicone resin emulsion, manufactured by BASF), AP4710 (acrylic-silicone resin emulsion, Showa Polymer) W-615, W-6020, W-6061, W-5661 (urethane resin emulsion, all manufactured by Mitsui Chemicals Polyurethanes), FE4300, FE4500, FE4400 (fluorine resin emulsion, all manufactured by Asahi Glass) Etc.

Two or more kinds of the resin emulsions may be used in combination, and by making the combination of resin emulsions appropriate, it is possible to improve image quality and image durability while ensuring ink storage stability.
The content of the resin emulsion is preferably 0.1% by mass to 20% by mass, and more preferably 0.1% by mass to 10% by mass as the resin solid content in the inkjet ink. When the content is less than 0.1% by mass, the amount of resin covering the pigment after landing on the recording medium is insufficient, and the scratch resistance is small. When the content is more than 20% by mass, the viscosity of the ink is high. This tends to make it difficult to print with an inkjet method.

  The other components are not particularly limited and may be appropriately selected as necessary. For example, an antifoaming agent, a pH adjuster, an antiseptic / antifungal agent, a rust inhibitor, an antioxidant, an ultraviolet absorber, Examples include oxygen absorbers and light stabilizers.

There is no restriction | limiting in particular as said antifoamer, According to the objective, it can select suitably, For example, a silicone type antifoamer, a polyether type antifoamer, a fatty-acid ester type | system | group antifoamer etc. are mentioned suitably. These may be used individually by 1 type and may use 2 or more types together. Among these, a silicone type antifoaming agent is preferable at the point which is excellent in the bubble-breaking effect.
Examples of the antiseptic / antifungal agent include 1,2-benzisothiazolin-3-one, sodium dehydroacetate, sodium sorbate, sodium 2-pyridinethiol-1-oxide, sodium benzoate, sodium pentachlorophenol, and the like. Can be mentioned.

  The pH adjuster is not particularly limited as long as it can adjust the pH to 7 or more without adversely affecting the ink to be prepared, and any substance can be used according to the purpose. Examples of the pH adjuster include amines such as diethanolamine and triethanolamine, hydroxides of alkali metal elements such as lithium hydroxide, sodium hydroxide and potassium hydroxide; ammonium hydroxide and quaternary ammonium hydroxide. Quaternary phosphonium hydroxide, alkali metal carbonates such as lithium carbonate, sodium carbonate, potassium carbonate, and the like.

Examples of the rust preventive include acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, dicyclohexylammonium nitrite, and the like.
Examples of the antioxidant include phenol-based antioxidants (including hindered phenol-based antioxidants), amine-based antioxidants, sulfur-based antioxidants, phosphorus-based antioxidants, and the like.

There is no restriction | limiting in particular as a physical property of the inkjet ink of this invention, According to the objective, it can select suitably, For example, it is preferable that a viscosity, surface tension, pH, etc. are the following ranges.
The viscosity at 25 ° C. is preferably 5 mPa · s to 20 mPa · s, and more preferably 6 mPa · s to 15 mPa · s. If the viscosity exceeds 20 mPa · s, it may be difficult to ensure ejection stability.

The surface tension is preferably 20 mN / m to 40 mN / m at 25 ° C. If the surface tension is less than 20 mN / m, bleeding on the recording medium becomes remarkable and stable jetting may not be obtained. If the surface tension exceeds 40 mN / m, ink penetration into the recording medium is sufficient. However, the drying time may be prolonged.
As said pH, 7-10 are preferable, for example.

-Inkjet recording device-
The ink of the present invention can be suitably used for various recording apparatuses using an ink jet recording system, such as an ink jet recording printer, a facsimile apparatus, a copying apparatus, a printer / fax / copier multifunction machine, and the like. In addition, it has an excellent characteristic that the head does not adhere to a recording apparatus including an ink jet head having an ink repellent layer containing a fluorine-based silane coupling agent or an ink repellent layer containing a silicone resin.

The outline of the ink jet recording apparatus used in the examples will be described below.
The ink jet recording apparatus shown in FIG. 1 has an apparatus main body (101), a paper feed tray (102) for loading paper mounted on the apparatus main body (101), and an image mounted on the apparatus main body (101). A paper discharge tray (103) for stocking the formed paper and an ink cartridge loading section (104) are provided. On the upper surface of the ink cartridge loading section (104), an operation section (105) such as operation keys and a display is arranged. The ink cartridge loading unit (104) has an openable / closable front cover (115) for attaching and detaching the ink cartridge (200). (111) is the upper cover, and (112) is the front surface of the front cover.

  In the apparatus main body (101), as shown in FIGS. 2 and 3, a guide rod (131), which is a guide member horizontally mounted on left and right side plates (not shown), and a stay (132), a carriage (133) ) Is slidably held in the main scanning direction, and is moved and scanned in the direction indicated by the arrow in FIG. 3 by a main scanning motor (not shown).

  The carriage (133) includes a plurality of recording heads (134) including four inkjet recording heads that discharge ink droplets of each color of yellow (Y), cyan (C), magenta (M), and black (Bk). Are arranged in a direction crossing the main scanning direction, and the ink droplet ejection direction is directed downward.

  As an inkjet recording head constituting the recording head (134), a piezoelectric actuator such as a piezoelectric element, a thermal actuator that utilizes a phase change caused by liquid film boiling using an electrothermal transducer such as a heating resistor, and a temperature change A shape memory alloy actuator using a metal phase change, an electrostatic actuator using an electrostatic force, or the like provided as energy generating means for discharging ink can be used.

  The carriage (133) is equipped with a sub tank (135) for each color for supplying ink of each color to the recording head (134). The sub tank (135) is supplied with ink according to the ink set of the present invention from the ink cartridge (200) of the present invention loaded in the ink cartridge loading section (104) via an ink supply tube (not shown). To be replenished.

  On the other hand, as a paper feeding unit for feeding the paper (142) stacked on the paper stacking unit (pressure plate) (141) of the paper feed tray (103), 1 sheet (142) is fed from the paper stacking unit (141). Opposite to the half-moon roller [sheet feeding roller (143)] for separating and feeding one sheet at a time, and the sheet feeding roller (143), a separation pad (144) made of a material having a large friction coefficient is provided, and this separation pad (144) is It is biased toward the paper feed roller (143).

  A conveying belt (151) for electrostatically adsorbing and conveying the paper (142) as a conveying unit for conveying the paper (142) fed from the paper feeding unit below the recording head (134). A counter roller (152) for conveying the paper (142) sent from the paper supply unit via the guide (145) between the conveying belt (151) and a paper (substantially vertically upward) ( 142) and a leading guide roller 153 urged toward the conveying belt (151) by the holding member (154). (155) and a charging roller (156) which is a charging means for charging the surface of the conveyor belt (151).

  The conveyance belt (151) is an endless belt, is stretched between the conveyance roller (157) and the tension roller (158), and can circulate in the belt conveyance direction. The transport belt (151) includes, for example, a surface layer serving as a sheet adsorbing surface formed of a resin material having a thickness of about 40 μm without resistance control, for example, a copolymer of tetrafluoroethylene and ethylene (ETFE), It has the same material as the surface layer and a back layer (medium resistance layer, earth layer) that has been subjected to resistance control by carbon. On the back side of the conveyance belt (151), a guide member (161) is arranged corresponding to the printing area by the recording head (134). As a paper discharge unit for discharging the paper (142) recorded by the recording head (134), a separation claw (171) for separating the paper (142) from the transport belt (151), and paper discharge A roller (172) and a paper discharge roller (173) are provided, and a paper discharge tray (103) is arranged below the paper discharge roller (172).

  A double-sided paper feeding unit (181) is detachably attached to the back surface of the apparatus main body (101). The double-sided paper feeding unit (181) takes in the paper (142) returned by the reverse rotation of the transport belt (151), reverses it, and feeds the paper again between the counter roller (152) and the transport belt (151). To do. A manual paper feed unit (182) is provided on the upper surface of the double-sided paper feed unit (181).

  In this ink jet recording apparatus, the sheet (142) is separated and fed one by one from the sheet feeding unit, and the sheet (142) fed substantially vertically upward is guided by the guide (145) and the transport belt (151). ) And the counter roller (152). Further, the leading end is guided by the conveying guide (153) and pressed against the conveying belt (151) by the leading end pressure roller (155), and the conveying direction is changed by about 90 °.

  At this time, the conveyance belt (157) is charged by the charging roller (156), and the paper (142) is electrostatically adsorbed to the conveyance belt (151) and conveyed. Therefore, by driving the recording head (134) according to the image signal while moving the carriage (133), ink droplets are ejected onto the stopped sheet (142) to record one line, and the sheet ( 142), the next line is recorded after a predetermined amount is conveyed. Upon receiving a recording end signal or a signal that the rear end of the paper (142) has reached the recording area, the recording operation is finished and the paper (142) is discharged to the paper discharge tray (103).

When a near-end ink remaining amount in the sub tank (135) is detected, a required amount of ink is supplied from the ink cartridge (200) to the sub tank (135).
In this ink jet recording apparatus, when the ink in the ink cartridge (200) of the present invention is used up, the casing of the ink cartridge (200) can be disassembled and only the ink bag inside can be replaced. Further, the ink cartridge (200) can supply ink stably even when the ink cartridge (200) is vertically placed and has a front loading configuration. Therefore, even when the upper part of the apparatus main body (101) is closed and installed, for example, even when it is stored in a rack or an object is placed on the upper surface of the apparatus main body (101), the ink The cartridge (200) can be easily replaced.

  Here, an example is described in which the present invention is applied to a serial (shuttle type) ink jet recording apparatus that is scanned by a carriage, but the present invention can be similarly applied to a line type ink jet recording apparatus having a line type head.

Next, the ink cartridge shown in FIGS. 4 and 5 will be described. After the ink cartridge (200) is filled into the ink bag (241) from the ink inlet (242) and exhausted, the ink inlet (242) is closed by fusion. In use, the needle of the apparatus main body is pierced into the ink discharge port (243) made of a rubber member and supplied to the apparatus.
The ink bag (241) is formed of a packaging member such as a non-permeable aluminum laminate film. The ink bag (241) is usually housed in a plastic cartridge case (244) and is detachably mounted on various ink jet recording apparatuses.

-Inkjet recording method-
The ink jet recording method in the present invention can be realized by using the above ink jet recording apparatus, but can be more effectively performed by superimposing black ink droplets and color ink droplets. As a result, the polyurethane compound and the isocyanate compound are reliably crosslinked with an increase in viscosity from the liquid state, the generation of bleeding can be suppressed, and an image having excellent fixability can be formed.

Examples of the present invention will be described below, but the present invention is not limited to these examples. The “parts” in the blending amounts are all “parts by weight”.
(Preparation of pigment dispersion 1)
Carbon black Nipex 60 (manufactured by Degussa) 15 parts Dispersant represented by the following structural formula (1) 5 parts Ion exchange water 80 parts

  When the above dispersant is dissolved by adding water, and then the pigment is mixed and stirred and sufficiently moistened, using a kneading apparatus filled with φ0.5 mm zirconia beads: Dino mill KDL A type (manufactured by WAB), Kneading was performed at 2000 rpm for 60 minutes. Next, the mill base was taken out and filtered through a 1 μm filter to obtain a black pigment dispersion Bk1 having a pigment concentration of 15%.

(Preparation of yellow dispersion Y1)
Carbon black I. A yellow dispersion Y1 was prepared in the same manner as described above except that Pigment Yellow 74 (HANSA Yellow 5GX01 manufactured by Clariant Japan) was changed.

(Preparation of magenta dispersion M1)
Carbon black I. A magenta dispersion M1 was prepared in exactly the same manner as described above except that it was changed to CI Pigment Red 122 (Jet Magenta DMQ manufactured by Ciba Specialty Chemicals).

(Preparation of cyan dispersion C1)
Carbon black I. A cyan dispersion C1 was prepared in exactly the same manner as above except that the pigment blue was changed to Pigment Blue 15: 4 (HELIOGEN Blue D7107 manufactured by BASF Japan).

(Preparation of pigment dispersion 2)
-Polymer synthesis-
(Polymer raw material 1)
Styrene 11.2 parts Acrylic acid 2.8 parts Lauryl methacrylate 12.0 parts Polyethylene glycol methacrylate 4.0 parts Styrene macromer AS-6 (manufactured by Toagosei Co., Ltd.) 4.0 parts Mercaptoethanol 0.4 part Mechanical stirrer, temperature The interior of the 1 L flask equipped with a total, a nitrogen gas inlet tube, a reflux tube and a dropping funnel was sufficiently substituted with nitrogen gas, and then the raw material 1 was charged and the temperature was raised to 65 ° C.
(Polymer raw material 2)
Styrene 100.8 parts Acrylic acid 25.2 parts Lauryl methacrylate 108.0 parts Polyethylene glycol methacrylate 36.0 parts Hydroxyethyl methacrylate 60.0 parts Styrene macromer AS-6 (manufactured by Toagosei Co., Ltd.) 36.0 parts mercaptoethanol 6 parts azobisdimethylvaleronitrile 2.4 parts methyl ethyl ketone 18.0 parts Then, the mixed solution of the raw material 2 was dropped into the flask heated up over 2.5 hours.
After completion of the dropwise addition, a mixed solution of 0.8 parts of azobisdimethylvaleronitrile and 18.0 parts of methyl ethyl ketone was dropped into the flask over 0.5 hours. After aging at 65 ° C. for 1 hour, 0.8 part of azobisdimethylvaleronitrile was added, and further aging was performed for 1 hour.
After completion of the reaction, 364.0 parts of methyl ethyl ketone was added to the flask to obtain 800 parts of a polymer (vinyl resin) solution having a concentration of 50%.
A dispersion was prepared using the following materials containing this polymer solution. That is, after sufficiently stirring the pigment and the polymer solution, they were kneaded 20 times using a three-roll mill (manufactured by Noritake Company: NR-84A). The obtained paste was put into 200 parts of ion-exchanged water and sufficiently stirred, and then methyl ethyl ketone and water were distilled off using an evaporator to obtain a black dispersion Bk2 having a pigment concentration of 15%.

(Dispersion material)
Carbon black Nipex 60 (Degussa) 26.0 parts Polymer solution 28.0 parts 1 mol / L aqueous potassium hydroxide 13.6 parts Methyl ethyl ketone 20.0 parts Ion-exchanged water 30.0 parts

(Preparation of yellow dispersion Y2)
Carbon black I. A yellow dispersion Y2 was prepared in exactly the same manner as described above except that it was changed to CI Pigment Yellow 74 (HANSA Yellow 5GX01 manufactured by Clariant Japan).

(Magenta dispersion M2)
Carbon black I. Magenta dispersion M2 was prepared in exactly the same manner as described above except that it was changed to CI Pigment Red 122 (Jet Magenta DMQ manufactured by Ciba Specialty Chemicals).

(Preparation of Cyan Dispersion C2)
Carbon black I. A cyan dispersion C2 was prepared in exactly the same manner as described above except that it was changed to CI Pigment Blue 15: 4 (HELIOGEN Blue D7107 manufactured by BASF Japan).

Black inks 1 to 4 and color inks 1 to 4 were produced according to the following description.
<Ink 1>
Black dispersion Bk1 40.0 parts urethane resin emulsion W-5661 (Mitsui Chemical Polyurethanes, solid content 35%)
8.6 parts Nonionic surfactant EP5035 (manufactured by Nippon Shokubai Co., Ltd.) 1.0 part glycerin 14.0 parts 1,3-butanediol 14.0 parts 2-ethyl-1,3-hexanediol 2.5 parts tri Ethanolamine 0.2 part antiseptic / antifungal LV (manufactured by Arch Chemicals Japan Co., Ltd.) 0.1 part ion exchanged water 19.6 parts After mixing and stirring the above components, the mixture was filtered through a filter having a pore size of 0.8 μm to obtain black ink Bk1 was obtained.

  A yellow ink Y1 was prepared in the same manner as described above except that the yellow dispersion Y1 was used instead of the black dispersion Bk1.

  A magenta ink M1 was produced in the same manner as described above except that the magenta dispersion M1 was used instead of the black dispersion Bk1.

  A cyan ink C1 was produced in the same manner as described above except that the cyan dispersion C1 was used instead of the black dispersion Bk1.

<Ink 2>
Black dispersion Bk1 40.0 parts Polyisocyanate compound WD-725 (manufactured by Mitsui Chemicals Polyurethanes Co., Ltd.) 0.3 part nonionic surfactant EP5035 (manufactured by Nippon Shokubai Co., Ltd.) 1.0 part glycerin 14.0 parts 1,3 -Butanediol 14.0 parts 2-Ethyl-1,3-hexanediol 2.5 parts Triethanolamine 0.2 parts Antiseptic / antifungal LV (manufactured by Arch Chemicals Japan) 0.1 parts Ion-exchanged water 27.9 Part After mixing and stirring the above components, the mixture was filtered with a filter having a pore size of 0.8 μm to obtain black ink Bk2.

  A yellow ink Y2 was produced in the same manner as described above except that the yellow dispersion Y1 was used instead of the black dispersion Bk1.

  A magenta ink M2 was prepared in the same manner as described above except that the magenta dispersion M1 was replaced with the black dispersion Bk1.

  A cyan ink C2 was produced in the same manner as described above except that the cyan dispersion C1 was used instead of the black dispersion Bk1.

<Ink 3>
Black dispersion Bk2 40.0 parts urethane resin emulsion W-6061 (Mitsui Chemical Polyurethanes, solid content 30%)
10.0 parts fluorosurfactant FS-300 (manufactured by DuPont, solid content 40%) 1.3 parts glycerin 15.0 parts 3-methyl-1,3-butanediol 15.0 parts 2,2,4 -Trimethyl-1,3-pentanediol 2.5 parts Triethanolamine 0.2 part Proxel LV (antiseptic / antifungal agent, manufactured by Arch Chemicals Japan) 0.1 part ion-exchanged water 15.9 parts After stirring, the mixture was filtered with a filter having a pore diameter of 0.8 μm to obtain black ink Bk3.

  A yellow ink Y3 was produced in the same manner as described above except that the yellow dispersion Y2 was used instead of the black dispersion Bk2.

  A magenta ink M3 was prepared in the same manner as described above except that the magenta dispersion M2 was used instead of the black dispersion Bk2.

  A cyan ink C3 was produced in the same manner as described above except that the cyan dispersion C2 was used instead of the black dispersion Bk2.

<Ink 4>
Black dispersion Bk2 40.0 parts Polyisocyanate compound WD-725 (manufactured by Mitsui Chemicals Polyurethanes Co., Ltd.) 0.3 parts fluorinated surfactant FS-300 (manufactured by DuPont, solid content 40%) 1.3 parts glycerin 15 0.0 part 3-methyl-1,3-butanediol 15.0 parts 2,2,4-trimethyl-1,3-pentanediol 2.5 parts triethanolamine 0.2 part proxel LV (preservative antifungal agent, (Manufactured by Arch Chemicals Japan) 0.1 part ion-exchanged water 25.6 parts The above components were mixed and stirred, and then filtered through a filter having a pore size of 0.8 µm to obtain black ink Bk4.

  A yellow ink Y4 was prepared in the same manner as described above except that the yellow dispersion Y2 was used instead of the black dispersion Bk2.

  A magenta ink M4 was prepared in the same manner as described above except that the magenta dispersion M2 was used instead of the black dispersion Bk2.

  A cyan ink C4 was produced in the same manner as described above except that the cyan dispersion C2 was used instead of the black dispersion Bk2.

<Ink 5>
Black ink Bk5, yellow ink Y5, magenta ink M5, respectively, except that the amount of addition of urethane resin emulsion W-5661 from ink 1 is 0.3 parts and the difference is ion exchange water. Cyan ink C5 was produced.

<Ink 6>
Black ink Bk6, yellow ink Y6, magenta ink M6, magenta ink M6, respectively, except that the addition amount of polyisocyanate compound WD-725 from ink 2 was 0.01 parts and the difference was ion exchange water. Cyan ink C6 was produced.

<Ink 7>
Black ink Bk7, yellow ink Y7, magenta ink M7, and cyan ink C7 were prepared in the same manner as ink 2, except that polyisocyanate compound WD-725 was removed from ink 2 and that portion was replaced with ion-exchanged water.

<Ink 8>
Black ink Bk, yellow ink Y8, magenta ink M8, and cyan ink C8 were respectively produced in the same manner as ink 3 except that polyurethane compound W-6061 was removed from ink 3 and that portion was replaced with ion-exchanged water.

  Recording was performed on commercially available copy paper with the colorless inks and ink combinations shown in Table 1. As the ink jet recording apparatus used, the printer IPSiO G707 (manufactured by Ricoh) having the structure shown in FIGS.

  Recording was performed on commercially available copy paper with the colorless inks and ink combinations shown in Table 1. As the ink jet recording apparatus used, the printer IPSiO G707 (manufactured by Ricoh) having the structure shown in FIGS.

  Recording was performed on commercially available copy paper with the colorless inks and ink combinations shown in Table 1. As the ink jet recording apparatus used, the printer IPSiO G707 (manufactured by Ricoh) having the structure shown in FIGS.

  Recording was performed on commercially available copy paper with the colorless inks and ink combinations shown in Table 1. As the ink jet recording apparatus used, the printer IPSiO G707 (manufactured by Ricoh) having the structure shown in FIGS.

  Recording was performed on commercially available copy paper with the colorless inks and ink combinations shown in Table 1. As the ink jet recording apparatus used, the printer IPSiO G707 (manufactured by Ricoh) having the structure shown in FIGS.

  Recording was performed on commercially available copy paper with the colorless inks and ink combinations shown in Table 1. As the ink jet recording apparatus used, the printer IPSiO G707 (manufactured by Ricoh) having the structure shown in FIGS.

[Comparative Example 1]
Recording was performed on commercially available copy paper with the colorless inks and ink combinations shown in Table 1. As the ink jet recording apparatus used, the printer IPSiO G707 (manufactured by Ricoh) having the structure shown in FIGS.

[Comparative Example 2]
Recording was performed on commercially available copy paper with the colorless inks and ink combinations shown in Table 1. As the ink jet recording apparatus used, the printer IPSiO G707 (manufactured by Ricoh) having the structure shown in FIGS.

[Comparative Example 3]
Recording was performed on commercially available copy paper with the colorless inks and ink combinations shown in Table 1. As the ink jet recording apparatus used, the printer IPSiO G707 (manufactured by Ricoh) having the structure shown in FIGS.

[Comparative Example 4]
Recording was performed on commercially available copy paper with the colorless inks and ink combinations shown in Table 1. As the ink jet recording apparatus used, the printer IPSiO G707 (manufactured by Ricoh) having the structure shown in FIGS.

(Evaluation)
The following evaluation was performed about each ink of the said Examples 1-6 and Comparative Examples 1-4.
[Evaluation 1: Color bleed]
Use a print pattern that prints black ink characters in solid image areas of magenta, cyan, and yellow color inks, and prints using My Paper (Ricoh) and POD Gloss 100 (Oji Paper Co., Ltd.) as test paper. went. The printing conditions were 100% duty, the recording density was 300 dpi, and one-pass printing.
The color bleed (bleeding) between the color ink and the black ink was visually determined based on the following evaluation criteria.
〔Evaluation criteria〕
○: No color bleeding occurs and black characters can be clearly recognized.
Δ: Color bleed is slightly generated and black characters are slightly blurred.
X: Color bleed occurs and black characters blur significantly.

[Evaluation 2: Scratch resistance]
Using My Paper (manufactured by Ricoh) as test paper, black alphanumeric characters consisting of four colors of black, yellow, magenta, and cyan were printed. Thereafter, the character part was rubbed once with a finger and judged according to the following evaluation criteria.
〔Evaluation criteria〕
○: Almost no change in character part and almost no ink mark on finger △: Character part is slightly distorted and ink mark is also slightly on finger ×: Almost no character can be recognized and ink mark on finger is considerable The evaluation results are shown in Table 2.

101 apparatus main body 102 paper feed tray 103 paper discharge tray 104 ink cartridge loading unit 105 operation unit 111 upper cover 112 front cover front surface 115 front cover 131 guide rod 132 stay 133 carriage 134 recording head 135 sub tank 141 paper placement unit 142 paper 143 Feed roller 144 Separation pad 145 Guide 151 Transport belt 152 Counter roller 153 Transport guide 154 Pressing member 155 Pressure roller 156 Charging roller 157 Transport roller 158 Tension roller 161 Guide member 171 Separating claw 172 Paper discharge roller 173 Paper discharge roller 181 Paper unit 182 Manual paper feed unit 200 Cartridge 241 Storage bag 242 Inlet 243 Outlet 244 Cartridge case

JP 2003-166183 A JP 2007-152149 A WO2006 / 129476 Japanese Patent No. 4001371

Claims (6)

  In an ink set comprising a black ink and at least one or more color inks, the black ink contains one of a polyurethane compound or a polyisocyanate compound having a hydroxyl group in the molecule, and the color ink is one of these compounds. An ink set comprising a polyisocyanate compound corresponding to any of the above or a polyurethane compound having a hydroxyl group in the molecule.   The ink set according to claim 1, wherein the polyurethane compound having a hydroxyl group is a self-emulsifying urethane resin emulsion.   The ink set according to claim 1, wherein the polyurethane compound having a hydroxyl group is contained in the ink by at least 0.1 wt% or more.   The ink set according to any one of claims 1 to 3, wherein the polyisocyanate compound is a water-dispersible isocyanate compound having a nonionic group.   The ink set according to claim 1, wherein the color ink comprises at least a cyan ink, a magenta ink, and a yellow ink.   Corresponding to any one of these compounds, black ink droplets containing either a polyurethane compound or a polyisocyanate compound having a hydroxyl group in the molecule in an ink set comprising a black ink and at least one or more color inks An ink jet recording method characterized by an increase in viscosity when color ink droplets containing a polyisocyanate compound or a polyurethane compound having a hydroxyl group in the molecule overlap in a liquid state.

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