JP2007063316A - Ink for ink jet, its production method, ink cartridge, ink jet device, image-forming method and image-formed article - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ink for ink jet, having excellent printing characteristics on plain paper and good storage stability, to provide its production method, to provide an ink cartridge, to provide an ink jet device, to provide an image-forming method, and to provide an image-formed article. <P>SOLUTION: This ink is obtained by mixing a pigment with a nonionic or anionic surfactant for dispersing the pigment to prepare a pigment dispersion, mixing the dispersion with a urethane resin emulsion having an average particle diameter of <10 nm, and then adding and mixing the mixture with a urethane resin emulsion having an average particle diameter of 10 to 200 nm. The ink is received in an ink cartridge, and then printed with an ink jet device 50 comprising a mechanism for carrying paper 52 with a paper-feeding motor 51, a method for reciprocating a carriage 54 with a carriage motor 53, a mechanism for driving a printing head 56 loaded on the carriage 54 to control the extrusion and dot formation of the ink, and a circuit 58 for controlling these members. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an inkjet ink having excellent printing characteristics on plain paper and excellent storage stability, a method for producing the same, an ink cartridge, an inkjet apparatus, an image forming method, and an image formed article.

The inkjet recording method is easy to make full color because the process is simpler than other recording methods, and there is an advantage that a high-resolution image can be obtained even with an apparatus having a simple configuration. As ink-jet inks, dye-based inks in which various water-soluble dyes are dissolved in water or a mixture of water and an organic solvent are used. Dye-based inks have excellent color clarity but are not resistant to light. Inferior in water resistance and water resistance, and also has a large blur on plain paper. On the other hand, a pigment-based ink in which carbon black or various organic pigments are dispersed is superior to a dye-based ink in terms of light resistance and water resistance, and is less liable for plain paper.
However, pigment-based inks tend to cause ejection defects due to aggregation and thickening of pigments compared to dye-based inks. There are roughly four types of pigment dispersions that are the raw materials for pigment-based inks: capsule type, self-dispersing type, polymer dispersing type, and surfactant dispersing type. In a capsule-type dispersion as disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2001-247800), an organic solvent is indispensable in the production process, which not only adversely affects the environment but also tends to increase the production cost. Further, the self-dispersing dispersion as disclosed in Patent Document 2 (Japanese Patent No. 3405817) not only has an adverse effect on the environment, but also requires the use of chemicals such as an oxidizing agent and a diazo coupling agent. In the case of a color organic pigment, the pigment is likely to dissolve (dyeation) due to the hydrophilic group introduced into the pigment, and the water resistance of the ink tends to be inferior. On the other hand, in the polymer dispersion type disclosed in Patent Document 3 (Japanese Patent No. 2714240), it takes a long time to disperse, so that the production cost tends to increase, and it is difficult to make the pigment fine particles.

In the surfactant dispersion type, the dispersion can be obtained simply by mixing the pigment and the dispersant, and dispersion can be achieved in a short time, and the production cost can be reduced. The storage stability of the ink tends to be inferior compared to the body. In recent years, in order to support high-speed printing on plain paper and improve fixability, high-concentration inks with increased solid content concentrations such as pigments and resin emulsions in the ink have been developed. Since the distance between the dispersed solids (pigments, resin emulsion) is shortened, the storage stability tends to be inferior to that of conventional pigment inks.
As a method for improving the storage stability by using a surfactant-dispersed dispersion, Patent Document 4 (Patent No. 3625595), Patent Document 5 (Patent No. 3390153), and Patent Document 6 (Japanese Patent Laid-Open No. 2003). As described in JP-A-96342), there is a method in which a surfactant and a polymer dispersant or emulsion particles are used in combination, but the storage stability can be improved. When a highly permeable surfactant is added to ensure quick drying in high-speed printing, the storage stability tends to be inferior. Further improvement in image quality such as image density and saturation is also demanded.
Patent Document 7 (Japanese Patent Application Laid-Open No. 2004-169008) discloses an ink jet recording ink comprising a pigment, water, a water-soluble organic solvent, a surfactant, and a polyurethane resin. The storage stability with the addition of the surfactant was insufficient.

JP 2001-247800 A Japanese Patent No. 3405817 Japanese Patent No. 2714240 Japanese Patent No. 3625595 Japanese Patent No. 3390153 JP 2003-96342 A JP 2004-169008 A

  An object of the present invention is to use an ink jet ink that uses a surfactant-dispersed dispersion excellent in production cost, has excellent printing characteristics on plain paper, and has good storage stability even in high-concentration and high-penetration inks. An object of the present invention is to provide a manufacturing method, an ink cartridge, an ink jet apparatus, an image forming method, and an image formed product.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors, in particular, by using together the urethane resin emulsion A having an average particle size of less than 10 nm and the urethane resin emulsion B having an average particle size of 10 nm to 200 nm. For the first time, the present inventors have found that storage stability and high image quality of plain paper can be achieved at a high level even in high-concentration and high-penetration inks.

The present invention is as follows.
1) It contains at least a pigment, a nonionic or anionic surfactant that disperses the pigment, a urethane resin emulsion A having an average particle size of less than 10 nm, and a urethane resin emulsion B having an average particle size of 10 nm to 200 nm. Ink for inkjet.
2) The ink-jet ink as described in 1) above, wherein the urethane resin emulsion A is ether-based.
3) The inkjet ink as described in 1) or 2) above, wherein the urethane resin emulsion B is ether-based or ester-based.
4) The inkjet ink according to any one of 1) to 3) above, wherein at least one of the urethane resin emulsion A or B is a self-emulsifying type containing a carboxyl group.
5) The inkjet ink according to any one of 1) to 4) above, wherein the content of the urethane resin emulsion B is larger than the content of the urethane resin emulsion A.
6) The inkjet ink according to any one of 1) to 5) above, wherein the content of the nonionic or anionic surfactant is larger than the content of the urethane resin emulsion A.
7) The inkjet ink according to any one of 1) to 6) above, wherein the content (solid content) of the urethane resin emulsion A with respect to the pigment is 3% by mass or more and 20% by mass or less.
8) The ink for inkjet according to any one of 1) to 7) above, wherein the total solid content concentration in the ink is 6% by mass or more and 25% by mass or less.
9) The inkjet according to any one of 1) to 8) above, which further contains another nonionic or anionic surfactant other than the nonionic or anionic surfactant that disperses the pigment. For ink.
10) The inkjet ink according to any one of 1) to 9) above, which contains one or more other resin emulsions C other than the urethane resin emulsions A and B.
11) The ink for ink jet recording according to 10), wherein the resin emulsion C is at least one selected from an acrylic resin, a styrene-acrylic resin, and an acrylic silicon resin.
12) A pigment dispersion is prepared by mixing a pigment and a nonionic or anionic surfactant that disperses the pigment. After the pigment dispersion and the urethane resin emulsion A having an average particle size of less than 10 nm are mixed, the average The method for producing an ink-jet ink as described in any one of 1) to 11) above, wherein the urethane resin emulsion B having a particle size of 10 nm to 200 nm and other materials are added and mixed as necessary.
13) An ink cartridge containing the ink-jet ink according to any one of 1) to 11).
14) An ink jet apparatus comprising a head for discharging the ink jet ink according to any one of 1) to 11).
15) An image forming method, wherein printing is performed using the ink jet apparatus described in 14).
16) An image formed product printed by the image forming method described in 15) above.

  According to the present invention, an inkjet ink excellent in printing characteristics on plain paper and excellent in storage stability even in a high-concentration and high-penetration ink, a manufacturing method thereof, an ink cartridge, an inkjet apparatus, an image forming method, and an image formed article are provided. Can be provided.

The inkjet ink of the present invention contains at least a pigment, a nonionic or anionic surfactant that disperses the pigment, a urethane resin emulsion A having an average particle size of less than 10 nm, and a urethane resin emulsion B having an average particle size of 10 nm to 200 nm. It is characterized by doing.
By using the urethane resin emulsion A having an average particle size of less than 10 nm, the aggregation and thickening of the pigment during ink storage can be suppressed even in a high-concentration and high-penetration ink. The urethane resin emulsion B having an average particle size of 10 nm or more and 200 nm or less is less susceptible to ink aggregation and thickening than the styrene-acrylic resin emulsions and acrylic-silicone resin emulsions disclosed in the prior art. The image quality at the time of printing can also be ensured. Therefore, by using the resin emulsions A and B in combination, it is possible to achieve both high storage stability and high image quality of plain paper even in high-concentration and high-penetration inks. Further, by using the resin emulsions A and B in combination, scratch resistance and marker resistance can be satisfied.

  Examples of the pigment used in the present invention include organic pigments such as azo, phthalocyanine, anthraquinone, dioxazine, indigo, thioindigo, perylene, isoindolenone, aniline black, azomethine, rhodamine B lake pigment, and the like. Examples of the inorganic pigment include carbon black, iron oxide, titanium oxide, calcium carbonate barium sulfate, aluminum hydroxide, barium yellow, bitumen, cadmium red, chrome yellow, and metal powder.

  More specifically, as the black pigment, carbon blacks (CI pigment black 7) such as furnace black, lamp black, acetylene black, channel black, or copper oxide, iron oxide (CI pigment) Examples thereof include black 11), metals such as titanium oxide, and organic pigments such as aniline black (CI Pigment Black 1).

  Examples of yellow pigments 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.

  Examples of magenta pigments 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, and the like.

  Examples of cyan pigments 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, 22, 56, 60, 63, 64, Bat Blue 4, Bat Blue 60, and the like.

Also, red, green, and blue for intermediate colors 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 the above pigments, carbon black is particularly preferable as the black pigment. Carbon black produced by the furnace method and the channel method has a primary particle size of 15 to 40 nm and a specific surface area of 50 to 300 m ² / g by the BET adsorption method. A DBP oil absorption of 40 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. As pigments, Pigment Yellow 13, 17, 55, 74, 93, 97, 98, 110, 128, 139, 147, 150, 151, 154, 155, 180, 185, Pigment Red 122, 202, 209, Pigment Blue 15: 3 and 15: 4 are preferred.

The average particle size of the pigment is not particularly limited, but is preferably 10 nm to 150 nm, more preferably 20 nm to 100 nm, and further preferably 30 nm to 80 nm. If the average particle diameter of the pigment exceeds 150 nm, not only the saturation of the printed image is lowered, but also thickening aggregation during ink storage and nozzle clogging during printing are likely to occur. When the particle size 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 in the present invention is a particle refractive index using a microtrack 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%. 1.51, particle density 1.4 g / cm ³ , solvent parameter is 50% average particle size (D50) measured at 23 ° C. using pure water parameters.

  The pigment concentration in the ink is preferably 2% by mass to 15% by mass, more preferably 3% by mass to 12% by mass, and even more preferably 5% by mass to 10% by mass. If the pigment concentration is less than 2% by mass, the coloring power is insufficient, so that the vividness of the image tends to be inferior. If the pigment concentration exceeds 15% by mass, not only the storage stability of the ink is lowered but also the image becomes dull. There is. Unlike the conventional inkjet ink, the ink of the present invention can ensure storage stability even when the pigment concentration is as high as 5% by mass or more.

The nonionic or anionic activator dispersant used to disperse the pigment can be appropriately selected according to the pigment type or the ink formulation. Nonionic surfactants include polyoxyethylene lauryl ether, polyoxyethylene myristyl. Polyoxyethylene alkyl ethers such as ether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether, polyoxyethylene oleyl ether, polyoxyethylene alkyl phenyl ether such as polyoxyethylene octyl phenyl ether, polyoxyethylene nonyl phenyl ether, poly Oxyethylene α-naphthyl ether, polyoxyethylene β-naphthyl ether, polyoxyethylene monostyryl phenyl ether, polyoxyethylene distyryl phenyl ether And ether, polyoxyethylene alkyl naphthyl ether, polyoxyethylene monostyryl naphthyl ether, polyoxyethylene distyryl naphthyl ether, polyoxyethylene polyoxypropylene block copolymer, and the like. Also used are surfactants in which a part of polyoxyethylene in the above surfactant is replaced with polyoxypropylene, and surfactants condensed with a compound having an aromatic ring such as polyoxyethylene alkylphenyl ether with formalin. it can.
The HLB of the nonionic surfactant is preferably from 12 to 19.5, more preferably from 13 to 19. If the HLB is less than 12, there is a tendency for the dispersion stability to deteriorate due to poor compatibility of the surfactant with an aqueous medium such as an aqueous medium. If the HLB exceeds 19.5, the surfactant is adsorbed on the pigment. Since it becomes difficult, dispersion stability tends to deteriorate.

  Anionic surfactants include polyoxyethylene alkyl sulfate, polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl phenyl ether sulfate, polyoxyethylene monostyryl phenyl ether sulfate, polyoxyethylene distyryl phenyl ether sulfate. , Polyoxyethylene alkyl ether phosphate, polyoxyethylene alkyl phenyl ether phosphate, polyoxyethylene monostyryl phenyl ether phosphate, polyoxyethylene distyryl phenyl ether phosphate, polyoxyethylene alkyl ether carboxylate , Polyoxyethylene alkylphenyl ether carboxylate, polyoxyethylene monostyryl phenyl ether carboxylate, polyoxyethylene distyrylpheny Ether carboxylate, naphthalenesulfonate formalin condensate, melanin sulfonate formalin condensate, dialkyl sulfosuccinate ester salt, alkyl sulfosulfosuccinate, polyoxyethylene alkyl sulfosuccinic acid disalt, alkyl sulfoacetate, α- Olefin sulfonates, alkylbenzene sulfonates, alkyl naphthalene sulfonates, alkyl sulfonates, N-acyl amino acid salts, acylated peptides, soaps, etc. are mentioned. Among these, polyoxyethylene alkyl ether, polyoxy Particularly preferred are sulfates or phosphates of ethylene alkylphenyl ether and polyoxyethylene distyrylphenyl ether.

  The addition amount of the nonionic or anionic surfactant is preferably 10% by mass or more and 50% by mass or less based on the pigment. When the addition amount of the surfactant-based dispersant is less than 10% by mass of the pigment, the storage stability of the pigment dispersion and the ink is lowered, or the dispersion takes extremely long time. When the addition amount exceeds 50% by mass, the viscosity of the ink is increased. Tends to be too high, and thus the discharge stability tends to decrease.

The particle size of the urethane resin emulsion A is preferably less than 10 nm, and more preferably 8 nm or less. When the particle diameter of the urethane resin emulsion A is 10 nm or more, the storage stability of the ink tends to be lowered. The particle size of the urethane resin emulsion B is preferably 10 nm or more and 200 nm or less, and more preferably 15 nm or more and 150 nm or less. When the particle diameter of the urethane resin emulsion B is less than 10 nm, the image density on plain paper tends to be lowered, and when it exceeds 200 nm, the ejection stability tends to be lowered.
The average particle size of the resin emulsion in the present invention is a microtrack UPA-150 manufactured by Nikkiso Co., Ltd., using a sample diluted with pure water so that the resin concentration in the measurement sample is 0.1% by mass, a particle refractive index of 1.51, The particle density is 1.4 g / cm ³ , and the solvent parameter is a 50% average particle diameter (D50) measured at 23 ° C. using the parameter of pure water.
As a method for isolating the urethane resin emulsions A and B from the ink, a known filtration technique can be used, and the urethane resin emulsions A and B can be separated by techniques such as ultrafiltration, precision membrane filtration, and crossflow filtration. Centrifugation and chromatographic methods may also be applicable.

The urethane resin emulsion in the present invention is obtained by polymerizing polyisocyanate and polyether polyol, polyester polyol, polycarbonate polyol, polylactone polyol and the like.
Examples of polyisocyanates include aliphatic diisocyanate compounds such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate, isophorone diisocyanate, hydrogenated xylylene diisocyanate, 1,4-cyclohexane diisocyanate, and 4,4′-dicyclohexylmethane diisocyanate. Cycloaliphatic 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 (including carbodiimide, uretdione and uretoimine) Metamorphic materials, etc.).
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 polyomega-hydroxycaproic acid polyol.
Polycarbonate polyols include propanediol- (1,3), butanediol- (1,4) and / or hexanediol- (1,6), diols such as diethylene glycol, triethylene glycol or tetraethylene glycol and phosgene, Included are those known per se, such as products obtained from reaction with diaryl carbonates such as diphenyl carbonate or cyclic carbonates such as ethylene or propylene carbonate. Also suitable are polyester carbonates obtained from the polyesters or polylactones described above and phosgene, diaryl carbonates or cyclic carbonates.

  Among the above urethane resins, the urethane resin emulsion A is particularly preferably an ether type, and the urethane resin emulsion B is particularly preferably an ether type or an ester type. When the urethane resin emulsion A is not ether type, sufficient storage stability cannot be ensured, so ink aggregation and thickening are likely to occur during high temperature storage. When the urethane resin emulsion B is other than ether type or ester type, ink aggregation during high temperature storage is likely to occur. There is a tendency to increase viscosity and decrease viscosity.

As the urethane resin emulsion A and / or B, a self-emulsifying urethane resin emulsion having a hydrophilic group such as a sulfonyl group, a carboxyl group, or polyethylene oxide is preferable, and a self-emulsifying urethane resin emulsion having a carboxyl group is particularly preferable. By introducing a hydrophilic group into the urethane resin emulsion, the storage stability can be further improved. Examples of the method for introducing a hydrophilic group into the urethane resin emulsion include a method in which monomers such as dimethylolacetic acid, dimethylolbutanoic acid, dimethylolpropionic acid, and dimethylolbutyric acid are added and copolymerized during synthesis.
When a self-emulsifying urethane resin emulsion having a carboxyl group or a sulfonyl group is used, a basic compound may be contained in the ink in order to enhance the dispersibility of the urethane resin in an aqueous medium. Such a basic compound is not particularly limited as long as it can disperse the urethane resin in an aqueous medium to be described later by blending, and a commonly used basic compound can be used. For example, alkylamines such as butylamine and triethylamine, alkanolamines such as monoethanolamine, diethanolamine, triethanolamine and triisopropanolamine, morpholine, aqueous ammonia, sodium hydroxide, lithium hydroxide, potassium hydroxide, aminomethylpropanediol, Examples thereof include aminoethylpropanediol and choline. Moreover, you may use buffer agents, such as a trishydroxylmethylaminomethane and a good buffer, as a base. The addition amount of the basic compound is appropriately set according to the physical properties and use amount of the urethane resin to be used and the pH suitable as the ink, and may be used alone or in combination of two or more.

The urethane resin emulsion A or B is produced by synthesizing an isocyanate-terminated prepolymer in a low-boiling solvent (acetone, etc.) that does not react with isocyanate groups, introducing hydrophilic groups with diamines, polyols, etc., and then diluting with water. A solution method that converts the solvent and distills off the solvent to obtain a urethane dispersion; a prepolymer method in which an isocyanate group-terminated prepolymer having a hydrophilic group introduced is first synthesized, dispersed in water, and then chain extended with an amine; Melt method, Method of using urethane prepolymer in emulsifier aqueous solution as water as chain extender, Sulfonating aromatic ring of urethane prepolymer having free isocyanate group obtained from hydrophobic polyol and aromatic polyisocyanate The method of passing through the process, the method of using blocked isocyanate, etc. It is known to people, but not particularly limited.
In particular, a urethane-based resin may be synthesized by a prepolymer method, and in this case, a low molecular weight polyhydroxy compound may be used. Examples of the low molecular weight polyhydroxy compound include glycols, alkylene oxide low molar adducts mentioned above as raw materials, trihydric alcohols such as glycerin, trimethylolethane, and trimethylolpropane, and alkylene oxide low molar adducts thereof. .
In the case of an aqueous urethane resin, a method is generally known in which a urethane prepolymer prepared in an organic solvent phase is phase-inverted and emulsified and further chain-extended in the aqueous phase. In this case, polyamines such as diamine are generally used as chain extenders. Specifically, the urethane prepolymer is subjected to water extension or di- or triamine extension after neutralizing or neutralizing acid groups derived from dimethylolalkanoic acid. Examples of polyamines used as chain extenders for amine extension include diamines and triamines. Specific examples thereof include hexamethylene diamine, isophorone diamine, hydrazine, and piperazine.

  Examples of the method for controlling the particle size of the urethane resin emulsion A or B include a method for changing the ratio of the carboxyl group-containing monomer and the polyol and a method for controlling the stirring strength and temperature during the polymerization.

As the content of the urethane resin emulsion in the ink, it is preferable that the content of the urethane resin emulsion B is larger than the content of the urethane resin emulsion A. The content in the present invention means the solid content concentration in the ink. If the content of the urethane resin emulsion B is less than the content of the urethane resin emulsion A, the image density and storage stability of plain paper tend to be lowered.
The ratio of the contents of the urethane resin emulsions A and B is preferably 1: 1 to 1:20, more preferably 1: 1.5 to 1:10, as the former: the latter. If the content ratio exceeds 1:20, the ejection stability of the ink tends to decrease.

  Further, it is preferable that the content of the nonionic or anionic surfactant is larger than the content of the urethane resin emulsion A contained in the ink. If the content of the nonionic or anionic surfactant-based dispersant is smaller than the content of the urethane resin emulsion A, the viscosity of the ink becomes too high and the ejection stability tends to be inferior.

  The addition amount of the nonionic or anionic surfactant is preferably 0.05% by mass or more and 10% by mass or less, more preferably 0.1% by mass or more and 5% by mass or less in the ink. If it is less than 0.05% by mass, sufficient penetrability cannot be obtained, so that blurring occurs at the boundary at the two-color overlapping portion, and if it exceeds 10% by mass, the compound itself may precipitate at a low temperature, resulting in poor reliability.

  The content of the urethane resin emulsion A with respect to the pigment is preferably 3% by mass or more and 20% by mass or less, and more preferably 5% by mass or more and 15% by mass or less. If the content of the urethane resin emulsion A with respect to the pigment is less than 3% by mass, it is difficult to ensure sufficient storage stability, and if it exceeds 20% by mass, the viscosity of the ink becomes too high and the ejection stability is poor. Tend.

The total solid content concentration in the ink is preferably 6% by mass or more and 25% by mass or less, more preferably 7% by mass or more and 20% by mass or less, and more preferably 8% by mass or more and 15% by mass or less. When the total solid content concentration is less than 6% by mass, the blur of the printed image tends to increase, and when it exceeds 25% by mass, the storage stability tends to deteriorate.
The total amount of solid content in the present invention is the total amount of components insoluble in a mixture such as water or water-soluble organic solvent contained in the ink, and includes pigments, resin emulsions, and the like. The method of calculating the total amount of the solid content concentration in the ink is to separate the ink by centrifuging the ink by sedimentation or suspension, and measuring the mass, or adding a flocculant to the ink to aggregate the solid content, And a method of measuring the mass after separating from the ink.

The non-ionic or anionic surfactant other than the nonionic or anionic surfactant that disperses the pigment in order to improve the permeability to paper and impart quick drying properties to the ink in the inkjet ink of the present invention. It is possible to further contain a surfactant. When these highly penetrating surfactants are added to the ink, the storage stability tends to be lowered. However, the ink jet ink of the present invention ensures the storage stability even when such a surfactant is added. Is possible.
Nonionic or anionic surfactants include polyoxyethylene alkyl ether acetate, dialkyl sulfosuccinate, polyoxyethylene alkyl ether, polyoxyethylene alkylphenyl ether, polyoxyethylene polyoxypropylene block copolymer, acetylene Examples include glycol surfactants and fluorine surfactants. Among these, nonionic surfactants having a plurality of hydrophobic groups or nonionic surfactants having branched hydrophobic groups tend to hinder the storage stability of the ink. Even in combination with these surfactants, storage stability can be ensured.

  In the present invention, it is possible to contain one or more other resin emulsions C other than the urethane resin emulsions A and B. The resin emulsion C is an acrylic acid polymer that is a polymer or copolymer of acrylic acid (or methacrylic acid) or a derivative thereof (for example, methyl acrylate, ethyl acrylate, methacrylic acid, or methyl methacrylate). , Styrene-acrylic resin, acrylic silicon resin, styrene-butadiene rubber (SBR), ethylene-vinyl acetate (EVA), acrylonitrile-butadiene rubber (NBR), or other rubber-based polymers, starch, modified starch, gelatin, casein, Or a natural polymer such as soybean protein, or a cellulose-modified polymer such as carboxymethylcellulose (CMC), hydroxyethylcellulose (HEC), or hydroxypropylcellulose (HPC), or And polyvinyl alcohol copolymers - polyvinyl alcohol (PVA), modified PVA, polyacrylamide, polyethylene, polyacetal resins, guar gum, polyesters, polyvinyl pyrrolidone, ethylene. Of these, acrylic resins, styrene-acrylic resins, and acrylic silicon resins are particularly preferable from the viewpoints of fixability, image quality, and storage stability.

The pH of the ink is preferably 5 or more and 12 or less, more preferably 6 or more and 11 or less, and further preferably 7 or more and 10 or less. If the pH is less than 5 or more than 12, aggregation and thickening tend to occur during storage of the ink. The pH in the present invention is a value measured at 25 ° C. with a pH meter HM-50V manufactured by Toa Denpa.
As a method for adjusting pH, ammonium hydroxide, quaternary ammonium hydroxide, quaternary phosphonium hydroxide, carbonic acid, as well as alkalis exemplified in the neutralization of carboxyl group or sulfonyl group of the urethane resin emulsion can be used. It is possible by adding an alkali metal carbonate such as lithium, sodium carbonate or potassium carbonate, an acid such as hydrochloric acid, sulfuric acid, nitric acid, acetic acid or carbonic acid, urea or the like.

The ink of the present invention can use water as a dispersion medium. The following water-soluble organic solvents can be used for the purpose of making the ink have desired physical properties, preventing the ink from drying, and improving the dissolution stability of each compound.
Alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, isobutyl alcohol, ethylene glycol, diethylene glycol, triethylene glycol, polyethylene glycol, propylene glycol, 1,2-propanediol, 1, 2-butanediol, 1,3-butanediol, 1,4-butanediol, 2,3-butanediol, 2-methyl-1,3-butanediol, 1,5-pentanediol, 1,6-hexanediol, Obtained by dehydration condensation of polyhydric alcohols such as glycerin, 1,2,6-hexanetriol, 1,2,4-butanetriol, 1,2,3-butanetriol, and petriol, and the polyhydric alcohol and the alcohol. Monoether derivatives and Ether derivatives, polyhydric alcohol phenyl ethers such as ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, N-methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 2-pyrrolidone, 1,3-dimethylimidazolide Non, nitrogen-containing heterocyclic compounds such as ε-caprolactam, amides such as formamide, N-methylformamide, N, N-dimethylformamide, ketones such as acetone and methylethylketone, monoethanolamine, diethanolamine, triethanolamine, triisopropanol Amines such as amine, monoethylamine, diethylamine, triethylamine, propylamine, butylamine, sulfur-containing compounds such as dimethylsulfoxyside, sulfolane, thiodiethanol, Propylene carbonate, ethylene carbonate, and γ-butyrolactone. These solvents are used alone or in combination with water.
Among these, particularly preferred are diethylene glycol, thiodiethanol, polyethylene glycol 200 to 600, triethylene glycol, glycerin, 1,2,6-hexanetriol, 1,2,4-butanetriol, petriol, 1,3- Butanediol, 2,3-butanediol, 1,4-butanediol, 2-methyl-1,3-butanediol, 1,5-pentanediol, N-methyl-2-pyrrolidone, N-hydroxyethylpyrrolidone, 2- Pyrrolidone, 1,3 dimethylimidazolidinone. By using these compounds, excellent effects can be obtained for the high solubility of the present compound and the prevention of poor jetting properties due to water evaporation.
The addition amount of the water-soluble organic solvent is preferably 10% or more and 50% or less on a mass basis. If the water-soluble organic solvent is less than 10%, the viscosity after drying increases, and if it exceeds 50%, not only the viscosity of the ink increases, but also the character quality tends to deteriorate when printed.

  Further, as a penetrant added for the purpose of adjusting the surface tension other than the surfactant added to the ink of the present invention, diethylene glycol monophenyl ether, ethylene glycol monophenyl ether, ethylene glycol monoallyl ether, diethylene glycol monophenyl ether, Alkyl and aryl ethers of polyhydric alcohols such as diethylene glycol monobutyl ether, propylene glycol monobutyl ether, triethylene glycol monobutyl ether, tetraethylene glycol chlorophenyl ether, 2-ethyl-1,3-hexanediol, 2,2,4-trimethyl- Diols such as 1,3-pentanediol and 2,2-dimethyl-1,3-propanediol, polyoxyethylene polyoxypropylene block Copolymers, lower alcohols such as ethanol, 2-propanol, and the like are mentioned. Particularly preferred are diethylene glycol monobutyl ether as polyhydric alcohol alkyl ether, 2-ethyl-1,3-hexanediol as diol having 6 or more carbon atoms, and 2,2,4-trimethyl 1,3-pentanediol. Diols are preferred because they are less likely to cause aggregation of water-insoluble colorants. The addition amount depends on the type and desired physical properties, but is 0.1 to 20% by mass, preferably 0.5 to 10% by mass. If it is less than 0.1% by mass, the permeability is insufficient, and if it is 20% by mass or more, the particle formation characteristics are adversely affected. In addition, the addition of these improves wettability to the ink jet head member and the recording device, improves the filling property, and makes it difficult for recording defects due to bubbles to occur.

In addition to the above materials, conventionally known additives can be added to the inkjet ink of the present invention.
For example, as a preservative and antifungal agent, sodium dehydroacetate, sodium sorbate, sodium 2-pyridinethiol-1-oxide, sodium benzoate, sodium pentachlorophenol, isothiazoline and the like can be used in the present invention.
Other chelating agents include, for example, sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uramil diacetate, and the like.
Examples of the rust inhibitor include acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropyl ammonium nitrite, pentaerythritol tetranitrate, dicyclohexyl ammonium nitrite, and benzotriazole.
In addition, it is possible to add a water-soluble ultraviolet absorber, a water-soluble infrared absorber, an antifoaming agent, a pH buffering agent and the like depending on the purpose.
In addition, a dye can be used together as necessary. As a preferable dye, those having excellent water resistance and light resistance among dyes classified into acid dyes, direct dyes, basic dyes, reactive dyes, and food dyes in the color index are used.

  As a method for producing the ink of the present invention, first, a pigment dispersion is prepared by mixing water, a pigment, the nonionic or anionic surfactant that disperses the pigment, and, if necessary, a water-soluble organic solvent. This preparation is performed by premixing with a stirring blade, a homogenizer, or a beadless disperser and then dispersing using a known disperser such as a sand mill, ball mill, dyno mill, roll mill, nanomizer, or homogenizer. Thereafter, it is desirable to mix the obtained pigment dispersion and the urethane resin emulsion A, and then add and mix the urethane resin emulsion B and other materials as necessary. If the urethane resin emulsion B and other materials are mixed before mixing the pigment dispersion and the urethane resin emulsion A, they may aggregate and thicken. Further, by filtering coarse particles with a pigment dispersion or ink using a filter, a centrifugal separator, or the like, it is possible to ensure ink ejection stability.

  The ink cartridge for storing the ink of the present invention is of a type that is filled in the cartridge and mounted on the carriage, or a bag-shaped type that is installed at a location away from the carriage and that supplies ink to the head by a pipe or the like. Either can be used.

Examples of the method for printing the ink include a continuous jet type and an on-demand type. As an on-demand type, any method such as a piezo method, a thermal ink jet method, and an electrostatic method can be used. For example, the present invention can be applied to an ink jet apparatus as shown in FIG.
As shown in FIG. 1, the ink jet apparatus (50) includes a mechanism for transporting paper (52) by a paper feed motor (51), and a carriage (54) opposed to a platen (55) by a carriage motor (53). A mechanism that reciprocates while driving, a mechanism that drives the print head (56) mounted on the carriage (54) to control ink ejection and dot formation, and a color ink cartridge (63) for supplying ink to the head. ) And black ink cartridge (65), a partition plate (64) for holding the cartridge, a paper feed motor (51), a carriage motor (53), a print head (56), and an operation panel (57) And a control circuit (58) that controls the exchange of the signals.
The mechanism for transporting the paper (52) as a recording medium includes a gear train that transmits the rotation of the paper feed motor (51) not only to the platen (55) but also to a paper transport roller (not shown). The mechanism for reciprocating the carriage (54) includes a slide shaft (59) that is laid in parallel with the platen (55) shaft and slidably holds the carriage (54), and a carriage motor (53). A pulley (61) that stretches an endless drive belt (60) therebetween, a position detection sensor (62) that detects the origin position of the carriage (54), and the like.
The control system is not shown in the figure, but a control circuit provided in the ink jet apparatus includes, for example, a well-known CPU, a P-ROM storing a program, a RAM, and a character generator (CG that stores a dot matrix of characters). In addition to this, an I / F dedicated circuit dedicated to interface with an external motor or the like, and a print head (56 ), A motor driving circuit for driving the paper feed motor (51) and the carriage motor (53), and the like. The image formed product printed by the method and the ink jet apparatus as described above is excellent in image density and saturation.

  EXAMPLES Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to the following example. In addition, with a part means a mass part.

Manufacturing method of pigment dispersion After premixing the pigment, surfactant, and water shown in Table 1 below, using a Dino-Mill manufactured by Ashizawa Finetech Co., Ltd., using 0.3 μm zirconia beads for 2 hours, separating the beads from the liquid and dispersing the pigment Liquids A to C (pigment concentration: 15% by mass, surfactant concentration: 3.75% by mass) were obtained.

  Using the pigment dispersions A to C described above, among the formulations of Examples 1 to 6 and Comparative Examples 1 to 4 described in Table 2, the pigment dispersion and the resin emulsion 1 were prepared, and after stirring, the remaining materials were used. After mixing and stirring, the mixture was filtered through a 0.8 μm filter to obtain an ink. Further, after vacuum deaeration, an ink cartridge for IPSiO G707 made by Ricoh was filled into an ink cartridge.

  The inks of Examples 1 to 6 and Comparative Examples 1 to 4 were stored in a sealed state at 50 ° C. for 7 days, and the rate of change in viscosity before and after storage was calculated. Ink cartridges filled with the inks of Examples 1 to 6 and Comparative Examples 1 to 4 were set in IPSiO G707, and a solid image was printed on plain paper Type 6200 (manufactured by Ricoh) in plain paper high-quality mode, and the optical density of the image (OD) was measured with X-Rite 938. The results are shown in Table 5 below.

  As described above, in Examples 1 to 6, the image density was high, and the storage stability was stable in other inks although a decrease in viscosity was observed in Example 3 using the carbonate-based polyurethane resin emulsion. On the other hand, in Comparative Examples 1 to 4, the image density and the storage stability could not be compatible.

  According to the present invention, an inkjet ink excellent in printing characteristics on plain paper and excellent in storage stability even in a high-concentration and high-penetration ink, a manufacturing method thereof, an ink cartridge, an inkjet apparatus, an image forming method, and an image formed article are provided. Can be provided.

It is a figure for demonstrating the inkjet apparatus which can be used for this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 50 Inkjet apparatus 51 Paper feed motor 52 Paper 53 Carriage motor 54 Carriage 56 Print head 58 Control circuit

Claims (16)

  It contains at least a pigment, a nonionic or anionic surfactant that disperses the pigment, a urethane resin emulsion A having an average particle size of less than 10 nm, and a urethane resin emulsion B having an average particle size of 10 nm to 200 nm. ink.   The inkjet ink according to claim 1, wherein the urethane resin emulsion A is ether-based.   The inkjet ink according to claim 1 or 2, wherein the urethane resin emulsion B is ether-based or ester-based.   The inkjet ink according to any one of claims 1 to 3, wherein at least one of the urethane resin emulsion A or B is a self-emulsifying type containing a carboxyl group.   The inkjet ink according to any one of claims 1 to 4, wherein the content of the urethane resin emulsion B is larger than the content of the urethane resin emulsion A.   The inkjet ink according to any one of claims 1 to 5, wherein the content of the nonionic or anionic surfactant is greater than the content of the urethane resin emulsion A.   The inkjet ink according to claim 1, wherein the content of the urethane resin emulsion A with respect to the pigment is 3% by mass or more and 20% by mass or less.   8. The ink-jet ink according to claim 1, wherein the total solid content concentration in the ink is 6% by mass or more and 25% by mass or less.   The inkjet ink according to claim 1, further comprising another nonionic or anionic surfactant other than the nonionic or anionic surfactant that disperses the pigment.   10. The ink-jet ink according to claim 1, comprising at least one resin emulsion C other than the urethane resin emulsions A and B. 11.   The inkjet ink according to claim 10, wherein the resin emulsion C is at least one selected from an acrylic resin, a styrene-acrylic resin, and an acrylic silicon resin.   A pigment dispersion is prepared by mixing a pigment and a nonionic or anionic surfactant that disperses the pigment, and after mixing the pigment dispersion and the urethane resin emulsion A having an average particle diameter of less than 10 nm, the average particle diameter is mixed. The method for producing an ink-jet ink according to any one of claims 1 to 11, wherein the urethane resin emulsion B of 10 nm to 200 nm and other materials are added and mixed as necessary.   An ink cartridge containing the ink-jet ink according to claim 1.   An ink jet apparatus comprising a head for discharging the ink jet ink according to claim 1.   15. An image forming method, wherein printing is performed using the ink jet apparatus according to claim 14. An image formed product printed by the image forming method according to claim 15.

Images