JP2009067858A - Ink jet ink and image forming method - Google Patents

Abstract

An inkjet ink having high saturation and density of an image formed with a pigment-based inkjet ink, excellent long-term storage stability of the ink, good ejection stability, and particularly capable of printing with no printing distortion. To provide.
In an ink including at least a resin fine particle dyed with a pigment, a dispersant, water, and a fluorescent dye, the resin fine particle dyed with a fluorescent dye is an emulsion polymer using at least a vinyl monomer as a raw material. The vinyl monomer is a group derived from a cyano group-containing vinyl monomer A, a hydroxyl group, a carboxyl group, an amino group, a carbamoyl group, a sulfonic acid group, a phosphoric acid group, and these functional groups. A vinyl monomer obtained by mixing a vinyl monomer B having one or more groups selected from the above and a vinyl monomer C other than the vinyl monomers A and B. An ink-jet ink, wherein the vinyl monomer B is 4.75% by weight or less in the monomer mixture.
[Selection figure] None

Description

  The present invention comprises resin fine particles dyed with a fluorescent dye, has high image density and image saturation, is easy to adjust delicate color tone, has excellent ink storage stability, and has excellent image water resistance, The present invention relates to an inkjet ink for business that can be printed by an ink jet printer having good ejection stability and no print bending.

  Conventionally, inks used in ink jet recording systems have been mainly used in which various water-soluble dyes are dissolved in water alone or in a solvent composed of water and a water-soluble solvent, and various additives are added as necessary.

  However, when printing is performed using such a dye-based ink, the water resistance of the recorded image on the recording material is poor, and if the water is spilled, the problem of bleeding of the dye in the recorded portion easily occurs, Since the light resistance is poor, there is a problem that when the recording portion is exposed to light, a change in color tone or a decrease in density occurs.

  In order to improve the above-mentioned problems of dye-based inks, it is known to apply so-called pigment-based inks using carbon black or various organic pigments instead of dyes as colorants to inkjet recording systems.

When printing is performed using pigment-based ink, the ink dried on the recording material is a pigment as a colorant. Good properties.
In addition, since pigments are less reactive to light than dyes, the light resistance of pigment-based inks is superior to that of dye-based inks.

Such pigment-based inks are generally produced by adding various additives as necessary to a pigment dispersion prepared by dispersing a mixture of a pigment, a liquid medium and a dispersant using a dispersing machine such as a ball mill or a sand mill. However, the pigment dispersion used in the ink for ink jet recording usually has a particle size level of 200 nm or less in order to prevent nozzle clogging in a printing apparatus (ink jet printer), sharpness of a printed image, secondary color reproducibility, and transparency. It is necessary to finely disperse the pigment particles in the pigment dispersion. Furthermore, it is known that if the particles are made fine to a level of 50 nm or less, an image having high saturation and high transparency close to that of a dye ink can be formed.
However, for example, in the case of quinacridone pigment, which is one of the pigments mainly used in the past in magenta, the image saturation increases to some extent due to the fine particles, but the saturation of the magenta image formed with dye ink is It does not reach.

As an attempt to improve the image saturation of the pigment ink, Patent Document 1 (Japanese Patent Laid-Open No. 10-130558) adds a fluorescent pigment to the ink in an amount of 0.1 wt% to 3 wt% with respect to the ink amount. Thus, it is disclosed that the saturation is improved by about 5%.
However, the ink created when a fluorescent pigment is added to a normal pigment in this way is in a very unstable dispersion state as a liquid, and when printing evaluation is performed with an ink jet printer using this ink, the printing is bent, Alternatively, there is a problem that when ink is set in a piezo ink jet printer and left for one month and then printed again, the ink is clogged and the ink cannot be supplied and printing cannot be performed.

On the other hand, one of the categories of inkjet printers is the business inkjet printer field.
The (viscous) ink used in such fields is gelled or gelled and dried, and immediately dried without oozing even on plain paper, allowing high-speed duplex printing. In order to satisfy such characteristics, a highly viscous (viscus) ink is used as the ink compared to the dye ink.
However, when such a highly viscous ink is used, the printing stability and low maintenance (long-term storage stability) tend to be poor compared to dye ink. On the other hand, since the ink uses a pigment as described above, it has not yet reached a point where a high-saturation and high-definition print image having the same level as that of a dye can be obtained.
In addition, when a problem occurs in a business inkjet printer, it needs to be repaired. Usually, an inkjet printer does not have an “on-site maintenance” system for visiting an office for repair. “If a customer has a problem with a printer, the customer can only send the printer to the repair center. During that time, the printer cannot be used, and business will be hindered.
Japanese Patent Application Laid-Open No. 62-148580 of Patent Document 2 discloses a cyano group-containing vinyl monomer (A).
Vinyl having 20 to 80% by weight, a vinyl monomer having one or more groups selected from hydroxy group, carboxyl group, amino group, carbamoyl group and groups derived therefrom, and vinyl having sulfonic acid group or salt thereof Particle size of 0 to 20 parts by weight obtained by emulsion polymerization of 0.5 to 20 parts by weight of a vinyl monomer (B) composed of a vinyl monomer and a monomer mixture composed of other vinyl monomers (C) A fluorescent ink obtained by dyeing an emulsion polymer of 5 microns or less with a fluorescent dye is described, and Japanese Patent Application Laid-Open No. 01-304163 of Patent Document 3 describes that acrylonitrile is 10 to 80% by weight, preferably 30 to 55%. An emulsion polymer having a particle size of 0.5 microns or less, obtained by emulsion polymerization of a monomer mixture consisting of methacrylic acid by weight, 0.5 to 20% by weight of (meth) acrylic acid, and the balance of styrene, was dyed with a fluorescent dye. Water-based fluorescent inks for writing instruments containing 30 to 70% of colored materials and 5 to 35% of hydrophilic organic solvents are described. However, these dye particles are dyed with dyes instead of conventional dye inks. The present invention relates to an ink used alone, not a pigment ink, and therefore does not disclose any technical matters regarding problems of a pigment-based inkjet ink and a solution to the problem.
We have already proposed an inkjet ink containing at least a resin fine particle (A) having an average particle size of 50 to 200 nm dyed with at least a pigment, a dispersant, water, and a fluorescent dye, and an emulsion of a self-emulsifying polyurethane (Patent Literature) The present invention relates to a further improvement of the ink described in Patent Document 2.

Japanese Patent Laid-Open No. 10-130558 JP-A-62-148580 JP-A-1-304163 Japanese Patent Application No. 2006-254143

  The present invention has been made in view of the above-mentioned problems, and the saturation and density of an image formed with a pigment-based inkjet ink are high, and the ink has excellent long-term storage stability and good ejection stability. An object of the present invention is to provide an ink jet ink that can be printed by an ink jet printer (particularly, an ink jet printer in the field of business ink jet) that is not particularly bent.

  In order to solve the above-mentioned problems, an ink jet ink according to the present invention is dyed with a fluorescent dye in a high-viscosity ink containing at least a pigment, a dispersant, water, a self-emulsifying polyurethane resin, and resin fine particles dyed with a fluorescent dye. The resin fine particle is an emulsion polymer using at least a vinyl monomer as a raw material, and the vinyl monomer includes a cyano group-containing vinyl monomer A, a hydroxyl group, a carboxyl group, an amino group, and a carbamoyl. A vinyl monomer B having one or two or more groups selected from a group derived from a group, a sulfonic acid group, a phosphoric acid group, and these functional groups, and the vinyl monomers A and B A vinyl monomer obtained by mixing a vinyl monomer C other than the above, and the vinyl monomer B is 4.75% or less in the monomer mixture.

That is, the said subject is solved by the structure of (1)-(22) of this invention shown below.
(1) In an ink containing resin fine particles dyed with at least a pigment, a dispersant, water, and a fluorescent dye, the resin fine particles dyed with a fluorescent dye are emulsion polymers using at least a vinyl monomer as a raw material, The vinyl monomer is composed of a cyano group-containing vinyl monomer A, a hydroxyl group, a carboxyl group, an amino group, a carbamoyl group, a sulfonic acid group, a phosphoric acid group, and a group derived from these functional groups. A vinyl monomer obtained by mixing a vinyl monomer B having one or more selected groups and a vinyl monomer C other than the vinyl monomers A and B; An inkjet ink, wherein the vinyl monomer B is 4.75% by weight or less in the monomer mixture.
(2) The inkjet ink according to (1), wherein the ink liquid has a viscosity of 7.000 mPas or more.
(3) The inkjet ink as described in (1) or (2) above, which contains alkanediol.
(4) The inkjet ink as described in (3) above, wherein the alkanediol is 2-ethyl-1.3-hexanediol.
(5) The inkjet ink according to any one of (1) to (4), wherein an average particle size of the resin fine particles dyed with the fluorescent dye is 50 to 200 nm.
(6) The inkjet ink as described in any one of (1) to (5) above, which contains self-emulsifying polyurethane resin particles.
(7) The inkjet ink according to any one of (1) to (6), wherein the self-emulsifying polyurethane resin particles have an average particle size of 50 nm or less.
(8) The content of the self-emulsifying polyurethane resin particles is from 0.1 to 5.0% by weight, and the inkjet use according to any one of (1) to (7) ink.
(9) The inkjet ink according to any one of (1) to (8), wherein the pigment has an average particle diameter of 10 to 200 nm.
(10) The inkjet ink according to any one of (1) to (9), wherein the pigment is dispersed with a surfactant.
(11) The inkjet ink as described in (10) above, wherein the surfactant is a nonionic surfactant.
(12) The inkjet ink as described in (11) above, wherein the surfactant is a compound represented by the following general formula (I).

（式中、Ｒは炭素数１〜２０のアルキル基、アリル基、アラルキル基を表わし、ｌは０〜７の整数を表わし、ｎは２０〜２００の整数を表わす。）
（１３）前記界面活性剤が、ＰＯＥ（ｎ＝４０）βナフチルエーテルであることを特徴とする前記第（１２）項に記載のインクジェット用インク。
（１４）前記第（１）項乃至第（１３）項のいずれかに記載のインクジェット用インクを含有することを特徴とするインクカートリッジ。
（１５）画像形成装置に着脱可能であることを特徴とする前記第（１４）項に記載のインクカートリッジ。
（１６）前記第（１）項乃至第（１３）項のいずれかに記載のインクジェット用インクによる画像が受容体に形成されていることを特徴とする画像担持媒体。
（１７）前記第（１）項乃至第（１３）項のいずれかに記載のインクジェット用インクを用いて受容体に画像を形成することを特徴とする画像形成方法。
（１８）前記画像形成装置がインクジェットプリンタであることを特徴とする前記第（１５）項に記載のインクカートリッジ。
（１９）インクジェットプリンタから受容体に前記第（１）項乃至第（１３）項のいずれかに記載のインクジェット用インクを吐出させ、受容体に画像を形成することを特徴とする画像形成方法。
（２０）前記インクジェットプリンタが、ピエゾ方式のインクジェットプリンタであることを特徴とする前記第（１９）項に記載の画像形成方法。
（２１）前記インクジェットプリンタが、サーマル方式のインクジェットプリンタであることを特徴とする前記第（１９）項に記載の画像形成方法。
（２２）前記受容体が紙であることを特徴とする前記第（１６）項に記載の画像担持媒体。

(In the formula, R represents an alkyl group having 1 to 20 carbon atoms, an allyl group, or an aralkyl group, l represents an integer of 0 to 7, and n represents an integer of 20 to 200.)
(13) The inkjet ink as described in (12) above, wherein the surfactant is POE (n = 40) β naphthyl ether.
(14) An ink cartridge comprising the ink-jet ink according to any one of (1) to (13).
(15) The ink cartridge as described in (14) above, which is detachable from the image forming apparatus.
(16) An image-bearing medium, wherein an image using the ink-jet ink according to any one of (1) to (13) is formed on a receptor.
(17) An image forming method, wherein an image is formed on a receptor using the inkjet ink according to any one of (1) to (13).
(18) The ink cartridge as described in (15) above, wherein the image forming apparatus is an ink jet printer.
(19) An image forming method, wherein an ink jet ink according to any one of (1) to (13) is ejected from an ink jet printer to a receiver to form an image on the receiver.
(20) The image forming method as described in (19) above, wherein the ink jet printer is a piezo ink jet printer.
(21) The image forming method as described in (19) above, wherein the ink jet printer is a thermal ink jet printer.
(22) The image bearing medium according to item (16), wherein the receiver is paper.

  As is clear from the following detailed and specific description, the ink-jet ink of the present invention has high image saturation, excellent ink stability, no ink clogging, no print bending, and excellent ejection stability. It has an excellent effect of being.

Hereinafter, the present invention will be described in detail.
According to the items (1) to (7), the saturation and density of the image are high, the color tone can be easily adjusted, the storage stability and the water resistance of the image are excellent, the ejection stability is good, and particularly the printing. An ink-jet ink that can be printed with an ink-jet printer without bending is provided.

Further, in the ink-jet ink of item (1), the resin fine particles dyed with the fluorescent dye of (A) are emulsion polymers using at least a vinyl monomer as a raw material, and the vinyl monomer Is selected from the group consisting of a cyano group-containing vinyl monomer A, a hydroxyl group, a carboxyl group, an amino group, a carbamoyl group, a sulfonic acid group, a phosphoric acid group, and a group derived from these functional groups. A vinyl monomer obtained by mixing a vinyl monomer B having a group of at least species and a vinyl monomer C other than the vinyl monomers A and B, and the vinyl monomer B is preferably 4.75% or less of the monomer mixture. If it exceeds 4.75%, the storage stability of the ink deteriorates and the ejection stability deteriorates.
Further, the proportion of the vinyl monomer C (A) in the monomer mixture is preferably 4.00% or less. By controlling the proportion of the vinyl monomer C in the monomer mixture to 4.00% or less, ink aggregation can be prevented and high-quality dyeing can be performed to provide a high-quality and uniform print image. .

  In order to prepare (A) of the present invention, a known method, for example, a method disclosed in Examples described in JP-A No. 2001-181544 may be used.

  In order to disperse the pigment with the surfactant, the pigment powder, water and the surfactant are premixed and then dispersed by a known method using a dispersing machine such as a sand mill or a dyno mill.

  The pigment dispersion thus obtained is mixed with the above-mentioned resin fine particles (A) dyed with a fluorescent dye, whereby the pigment dispersion does not aggregate and the colorant fine particles are in a stable state. In addition, aggregation of the powders is prevented, and the ink is kept in a stable viscosity state.

The ink-jet ink using a mixture prepared by using the above-described vinyl monomer B other than the range of 4.75% or less in the monomer mixture has an unstable dispersion liquid composition and Become.
As this model, a case where a pigment dispersion solution dispersed with a dispersant and resin fine particles dyed with a fluorescent dye are mixed is assumed.
Pigments are usually insoluble in water and are dispersed in an aqueous solution by a dispersant.
Next, when a highly hydrophilic resin (the ratio of the hydrophilic resin is increased when the amount of acrylic acid is large) is mixed therewith, the fine pigment particles having a good dispersion state with time. A model has been estimated in which the resin particles dyed with the fluorescent dye are entangled with the hydrophilic resin portion and gradually aggregate.
Ink-jet ink using a mixture prepared using resin fine particles (A) in which the vinyl monomer B is in a range of 4.75% or less of the monomer mixture is a resin dyed with a fluorescent dye. The fine particles (A) and the pigment dispersion are placed in an optimum stable state to prevent aggregation, and aggregation is prevented.

The ink-jet ink (viscous ink) of the above item (2) lands on paper or becomes GEL, dries and dries even on plain paper, and can be quickly dried to enable high-speed duplex printing.
The viscosity of the ink is preferably 7.000 mPas or more, more preferably 7.500 mPas or more. When the viscosity of the ink is less than 7.000 mPas, drying on paper is slow, and the color density per unit area is low, so that the image density is lowered.

According to the inkjet ink of item (3) or (4), a pigment-based inkjet ink having high image saturation is provided.
The content of alkanediol is preferably 0.2 to 10% by weight, more preferably 0.3 to 8% by weight. When the content of alkanediol is less than 0.2% by weight, the image saturation is lowered, and when it is more than 10% by weight, the storage stability of the ink is deteriorated.

  The alkanediol is not particularly limited, but preferably 1,2-hexanediol, 1,2-heptanediol, 1,3-heptanediol, 2-methyl-1,3-hexanediol, 2- Butyl-2-ethyl-propanediol, and the like, more preferably 2-ethyl-1,3-hexanediol.

The ink jet ink of item (5) will be described in detail. The average particle size of (A) is preferably 50 to 200 nm. If the thickness is less than 50 nm, the fluorescence intensity decreases, so that the saturation of the image is lowered.
Furthermore, it is preferable that the average particle diameter of (A) is 70-150 nm. By setting the average particle diameter to 70 to 150 nm, irregular reflection of the pigment particles can be prevented, and a printed image having a uniform density can be provided.

The ink-jet ink of item (6) will be described in detail. The self-emulsifying polyurethane is preferably an anionic type.
Emulsions of polyurethane resins are obtained by emulsifying a relatively hydrophilic ordinary polyurethane resin using an emulsifier on the outside, and by introducing a functional group that functions as an emulsifier into the resin itself by means such as copolymerization. There are self-emulsifying emulsions, and an emulsion resin of an anionic self-emulsifying polyurethane that always has excellent dispersion stability in various combinations with pigments and dispersants.
In this case, the polyurethane resin is more preferably an ether type than a polyester type and a polycarbonate type in terms of pigment fixing and dispersion stability.
When the self-emulsifying polyurethane is not an anionic type, the stability of the liquid is deteriorated.

  The ink-jet ink of item (7) will be described in detail. The average particle size of the polyurethane emulsion is preferably 50 nm or less. If the average particle size is larger than 50 nm, the ink liquid is undesirably precipitated.

  Describing in detail with respect to the inkjet ink of item (8), the addition amount of the polyurethane emulsion is preferably 0.1 to 5.0% by weight as the polyurethane solid content. When the amount is less than 0.1% by weight, the polyurethane component adsorbed to the pigment is small, and the pigment adsorbs more and the viscosity of the liquid increases. When it is more than 5.0% by weight, the stability of the liquid is deteriorated due to adhesion between polyurethanes.

In the inkjet ink of item (9), the average particle size of the pigment is preferably 10 to 200 nm, more preferably 20 to 100 nm. When the average particle diameter is smaller than 10 nm, dispersion for a long time is required, and the storage stability of the ink also deteriorates. When the average particle diameter exceeds 200 nm, not only the image saturation is lowered, but also nozzle clogging is increased, and ink ejection stability is deteriorated.
In addition, the average particle diameter of the pigment in this invention has shown the value measured by Nikkiso Co., Ltd. Microtrac UPA.

  According to the ink-jet inks of the items (10) to (13), a pigment-based ink-jet ink is further provided in which the foaming of the ink is further suppressed and the image saturation is high.

As the surfactant, an anionic, nonionic, cationic or amphoteric surfactant can be used.
Anionic surfactants include fatty acid salts, alkyl sulfate salts, alkyl aryl sulfonates, alkyl naphthalene sulfonates, dialkyl sulfonates, dialkyl sulfosuccinates, alkyl diaryl ether disulfonates, alkyl phosphates, Examples include polyoxyethylene alkyl ether sulfate, polyoxyethylene alkyl aryl ether sulfate, naphthalenesulfonic acid formalin condensate, polyoxyethylene alkyl phosphate ester salt, glycerol borate fatty acid ester, polyoxyethylene glycerol fatty acid ester, etc. The
Nonionic surfactants include polyoxyethylene alkyl ether, polyoxyethylene alkyl aryl ether, polyoxyethylene oxypropylene block copolymer, sorbitan fatty acid ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene sorbitol fatty acid ester, glycerin fatty acid ester And polyoxyethylene fatty acid ester, polyoxyethylene alkylamine, fluorine-based, silicon-based and the like.
Examples of the cationic surfactant include alkylamine salts, quaternary ammonium salts, alkylpyridinium salts, alkylimidazolium salts and the like.
Examples of amphoteric surfactants include alkylbetaines, alkylamine oxides, phosphadylcholines, and the like.
Among these, nonionic surfactants are more preferably used, and particularly the compounds of the above general formula (I), among which POE (n = 40) β naphthyl ether can be particularly preferably used.

The fluorescent dye used in the present invention can be selected from various dye groups such as base dyes (including cathylon dyes), direct dyes, fluorescent whitening dyes, and more particularly one or more daylight fluorescent dyes and daylight fluorescent dyes. It is effective to use together with ordinary dyes (non-fluorescent dyes), but is not limited thereto.
Specifically, BASIC YELLOW 1, BASIC YELLOW 40, BASIC RED 1, BASIC RED 13, BASIC VIOLET 7, BASIC VIOLET 10, BASIC ORANGE 22, BASIC BLUE 7, BASIC BALE 7 1, DIRECT YELLOW 85, DIRECT ORANGE 8, DIRECTRED 9, DIRECT BLUE 22, DIRECT GREEN 6, FLUORESENT BRIGHTENING AGENT 55, FLUORESCENT BRIGHTENING WLU 52 ELLOW 40, BASIC RED1, BASIC VIOLET 10, FLUORESCENT BRIGHTENING WHITEX WS 52 is preferred.

  Coloring with these dyes can be performed either during emulsion polymerization or after polymerization. With regard to the conditions, it is preferable to leave it under stirring at 40 to 110 ° C. for 1 to 5 hours under atmospheric pressure or under pressure. The amount of the dye used is 0.01 to 100 parts by weight of the emulsion polymer (solid content). 10 to 10 parts by weight is preferable, and 0.1 to 5 parts by weight is more preferable.

The ink-jet ink of the present invention comprises a pigment as a colorant.
Specific examples of pigments used in magenta ink include C.I. I. Pigment Red 5, 7, 12, 48 (Ca), 48 (Mn), 57 (Ca), 57: 1, 112, 122, 123, 146, 168, 176, 184, 185, 202, 209, Pigment Violet 19 Etc.

  In the present invention, the pigment may be a so-called self-dispersing pigment (surface-treated pigment) having a water dispersibility-imparting group on its surface and capable of stably maintaining a dispersed state even without a dispersant, or the entire pigment surface. A so-called capsule type pigment (water-dispersible polymer-containing pigment) that can be coated with a polymer and can stably maintain a dispersed state without a dispersant, or a pigment dispersed with a dispersant may be used.

In the present invention, the pigment is preferably added to the ink as a pigment dispersion dispersed by a surfactant.
As the surfactant, a nonionic surfactant is preferable, and a compound represented by the following general formula (I) is more preferable.

（式中、Ｒは炭素数１〜２０のアルキル基、アリル基、アラルキル基を表わし、ｌは０〜７の整数を表わし、ｎは２０〜２００の整数を表わす。）

(In the formula, R represents an alkyl group having 1 to 20 carbon atoms, an allyl group, or an aralkyl group, l represents an integer of 0 to 7, and n represents an integer of 20 to 200.)

The ink for ink jet recording of the present invention uses water as a liquid medium, but a water-soluble organic solvent is added as a wetting agent for preventing the ink from drying. The use of the water-soluble organic solvent also serves to make the ink have desired physical properties (viscosity) and to improve the dissolution stability of the colorant.
In addition, in the present invention, an appropriate water-soluble organic solvent is selected in order to control image quality and printing stability with an ink in which resin fine particles dyed with a fluorescent dye and a pigment are mixed.

In addition to the water-soluble organic solvent, a pH adjuster, preservative, resin, and the like may be used as necessary for the inkjet ink in the present invention.
In the present invention, examples of the water-soluble organic solvent that can be added to the ink for inkjet when dispersing carbon black include, for example, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl. C1-C4 alkyl alcohols such as alcohol and tert-butyl alcohol; Amides such as dimethylformamide and dimethylacetamide; Ketones or ketone alcohols such as acetone, methyl ethyl ketone and diacetone alcohol; Ethers such as tetrahydrofuran and dioxane Ethylene glycol, propylene glycol, 1,2-propanediol, 1,2-butanediol, 1,3-butanediol, methyl-1,3-butanediol, 1,4-butanediol, Polyhydric alcohols such as diethylene glycol, triethylene glycol, 1,2,6-hexanetriol, thiodiglycol, hexylene glycol and glycerin; polyalkylene glycols such as polyethylene glycol and polypropylene glycol; ethylene glycol monomethyl (or ethyl) Lower alkyl ethers of polyhydric alcohols such as ether, diethylene glycol methyl (or ethyl) ether, triethylene glycol monomethyl (or ethyl) ether; alkanolamines such as monoethanolamine, diethanolamine and triethanolamine; N-methyl-2 -Pyrrolidone, 2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone and the like.
For ink-jet ink, among the above water-soluble organic solvents, polyhydric alcohols such as diethylene glycol, 1,3-butanediol, 3-methyl-1,3-butanediol, or triethylene glycol monomethyl (or ethyl) ether A lower alkyl ether of a polyhydric alcohol is preferred.
In addition, the content of the water-soluble organic solvent in the ink jet ink is preferably 50% by weight or less in consideration of environmental properties and the like.

In the inkjet ink of the present invention, the water can be pure water such as ion exchange water, ultrafiltration water, reverse osmosis water, distilled water, or ultrapure water.
In addition, the use of water sterilized by ultraviolet irradiation or addition of hydrogen peroxide is preferable because generation of mold and bacteria can be prevented when the ink is stored for a long period of time.

  As the PH buffer used in the present invention, aminoethanesulfonic acid, 2-aminoethanesulfonic acid, 2-aminoethyl sulfate ester, N-acetyl-L-cysteine, catechol, pyrogallol, o-phenolsulfonic acid, p-phenol Sulfonic acid, phloroglucinol, resorcinol, asparagine, arginine, L-allothreonine, ornithine, ornithine hydrochloride, glutathione (reduced form), glutathione (oxidized form), glutamine, cystine, cysteine, 3,4-dihydroxyphenylalanine, citrunin , L-serine, DL-serine, tyrosine, tryptophan, L-threonine, DL-threonine, histidine, phenylalanine, homocysteine, DL-methionine, L-methionine, lysine, lysine hydrochloride, 4-amino Lysine, pyridoxal, pyridoxine hydrochloride, morpholine, inosine, uracil, guanine, guanosine, hypoxanthine, purine, N, N-bis (2-hydroxyethyl) -2-aminoethanesulfonic acid, 3-morpholinopropanesulfonic acid, [ N-tris (hydroxymethyl) methyl-2-amino] ethanesulfonic acid, N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid, piperazine-N—N′-bis (2-hydroxypropane)- 3-sulfonic acid, 3- [N- (trishydroxymethyl) methylamino] -2-hydroxypropanesulfonic acid, 3- [N, N-bis (2-hydroxyethyl) amino] -2-hydroxypropanesulfonic acid N-2′-hydroxyethylpiperazine-N-2-hydroxypropane-3-sulfo Acid, N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid, tris (hydroxymethyl) aminomethane, N- [tris (hydroxymethyl) methyl] glycine, glycylglucin, N, N-di (2-hydroxyethyl) Glycine, N- [tris (hydroxymethyl) methyl] -3-aminopropanesulfonic acid, diethanolamine, ethanolamine, 2-amino-2-methyl-1,3-propanediol, 2-amino-2-ethyl-1,3 -Propanediol 3-[(1.1 dimethyl-2hydroxyethyl) amino] -2hydroxypropanesulfonic acid, 2-cyclohexylaminoethanesulfonic acid, N-cyclohexyl-2-hydroxy-3-aminopropanesulfonic acid, 3- Examples include cyclohexylaminopropane sulfonic acid In particular, 3-[(1.1 dimethyl-2hydroxyethyl) amino] -2hydroxypropanesulfonic acid, 2-cyclohexylaminoethanesulfonic acid, N-cyclohexyl-2-hydroxy-3-aminopropanesulfonic acid, 3-cyclohexylaminopropanesulfonic acid is particularly preferred.

  The addition amount of the PH buffer is 0.001% to 10%, preferably 0.005% to 5%, more preferably 0.05% to 2%. If the amount of the PH buffer is less than 0.001%, the effect of suppressing the change in PH is small, and if it exceeds 10%, the viscosity of the ink tends to increase.

The average particle diameter of the polyurethane resin particles in the present invention is a value measured with a Nikkiso Co., Ltd. Microtrac UPA at a sample concentration of 0.1%, and the image density and saturation are values measured with an X-rite densitometer. Yes.
The viscosity of the ink was measured at a liquid temperature of 25 ° C. using an E-type viscometer RE-500 manufactured by Toki Sangyo Co., Ltd.

  Examples of the means for printing using the inkjet ink of the present invention include a printing method using an inkjet printer (inkjet printer) having a continuous jet type or on-demand type recording head. Note that examples of the on-demand type include a piezo method, a thermal ink jet method, and an electrostatic method.

  Further, the present invention relates to the configuration of an ink cartridge containing the ink composition of the present invention, the configuration of an ink jet printing apparatus that performs recording by discharging the ink composition of the present invention, and the image forming method in the printing apparatus. By referring to known techniques in the technical field, such as those disclosed in Japanese Patent Application Laid-Open No. 2000-198958, it can be easily implemented.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further in detail, this invention is not limited to these Examples at all. In addition, the number of parts in an Example represents a weight part.

Example 1
A 2 L flask was equipped with a condenser, a thermometer, a 500 ml separatory funnel for introducing monomers and a stirrer, and set in a water bath.
Next, 440 ml of water, 8.5 g of Na dodecylbenzenesulfonate, and 7 g of nonionic surfactant Emulgen LS-110 (manufactured by Kao Corporation) were placed in the flask, and the internal temperature was raised to 80 ° C. . Next, after charging 2.1 g of potassium persulfate into the heated contents, a monomer solution in which 140 g of acrylonitrile, 120 g of styrene and 10 g of acrylic acid were mixed and stirred was stirred into the flask from the above separatory funnel. The solution was added dropwise over 3 hours, and the polymerization was completed in 4 hours.
200 g of water, 0.3 g of Rhodamine F3B (“BANISOL RED 560” manufactured by BASF), 2.0 g of Rhodamine F4G (“BANISOL RED 485” manufactured by BASF), and a special polycarboxylic acid were obtained. Type polymer surfactant (“Demol EP” manufactured by Kao Corporation) was added under stirring at room temperature, mixed uniformly, then gradually heated, and dyed at 85 ° C. for 1 hour. Then, a clear peach-colored fine particle dispersion having an average particle diameter of 60 nm was obtained.
The fine particle dispersion was adjusted to moisture to obtain a fluorescent fine particle dispersion (F) having a solid concentration of 40%.

Next, after premixing the mixture having the following constitution, it was circulated and dispersed for 20 hours in a disk type bead mill (KDL type, using 0.3 mmφ zirconia balls) to obtain a pigment dispersion (A) having an average particle size of 95.0 nm. It was.
Pigment Red 122 151 parts (manufactured by Ciba Specialty Chemicals, Irgaphore Magenta DMQ)
POE (n = 40) β naphthyl ether 57 parts Distilled water 702 parts

After adding the self-emulsifying anionic polyether-type polyurethane emulsion of (ii) to the pigment dispersion (A) obtained by the above method in the following quantitative ratio, the mixture is sufficiently stirred for 30 minutes, and the pigment dispersion (B) did.
(I) Pigment dispersion (A) 34.0 parts (ii) Self-emulsifying anionic polyether type polyurethane emulsion 10.0 parts
(Takelac W-5025 manufactured by Mitsui Takeda Chemical Co., Ltd.
(Solid content = 30.0%, average particle size = 20.3 nm)
The fluorescent fine particle dispersion (F) was added to the pigment dispersion (B) obtained by the above method in the following quantitative ratio, and then sufficiently stirred for 30 minutes to obtain a dispersion (C).
(I) 33.0 parts of pigment dispersion (B) (ii) 30.0 parts of fluorescent fine particle dispersion (F) having a solid concentration of 40%

Thereafter, an ink liquid was prepared from the following ink material (1), stirred for 30 minutes, filtered through a membrane filter having a pore size of 0.8 μm, and vacuum deaerated to obtain an ink jet ink of the present invention.
・ Ink material (1)
(Iii) Glycerol 15.0 parts (iv) Diethylene glycol 5.0 parts (v) 1,3-heptanediol 2.0 parts (vi) Distilled water 4.0 parts The viscosity of the ink thus prepared is 8. It was 0 mPas, and the ratio of the vinyl monomer B in the monomer mixture was 3.70% by weight.

(Example 2)
An ink-jet ink of the present invention was obtained in the same manner as in Example 1 except that 2.0 parts of 1,2-hexanediol was used in Example 1.
The viscosity of the ink thus prepared was 7.6 mPa s, and the ratio of the vinyl monomer B in the monomer mixture was 3.70% by weight.

(Example 3)
An inkjet ink of the present invention was obtained in the same manner as in Example 1 except that 2.0 parts of 2-methyl-1,3-hexanediol was used in Example 1.
The viscosity of the ink thus prepared was 7.7 mPas, and the ratio of the vinyl monomer B in the monomer mixture was 3.70%.

Example 4
An inkjet ink of the present invention was obtained in the same manner as in Example 1, except that 2.0 parts of 2-ethyl-1,3-hexanediol was used in Example 1.
The viscosity of the ink thus prepared was 7.5 mPas, and the ratio of the vinyl monomer B in the monomer mixture was 3.70% by weight.

(Comparative Example 1)
An inkjet ink was obtained in the same manner as in Example 1 except that 15 g of acrylic acid in Example 1 was used. The viscosity of the ink thus prepared was 8.2 mPas, and the ratio of the vinyl monomer B in the monomer mixture was 5.45% by weight.

(Comparative Example 2)
An inkjet ink was obtained in the same manner as in Example 2 except that 15 g of acrylic acid in Example 1 was used. The viscosity of the ink thus prepared was 7.6 mPas, and the ratio of the vinyl monomer B in the monomer mixture was 5.45% by weight. (Low density image)

The inkjet ink thus obtained was printed on plain paper (X-4024) with a piezo inkjet printer EM-930C manufactured by EPSON.
Next, a plain paper print image with EM-930C was measured with an Xrite densitometer, and image saturation was calculated. The results are shown in Table 1.
The ink-jet ink thus obtained was set in a piezo-type ink-jet printer EM-930C manufactured by EPSON and allowed to stand for one month. Thereafter, printing was performed in the same manner as described above.
At this time, ink could not be supplied and printing was indicated as ink clogging.
In Table 1, the saturation of an image refers to the distance from the origin on the chromaticity diagram when the solid image of the image sample is measured with an Xrite densitometer and plotted on the chromaticity diagram.

  Next, 200 sheets of a solid image test pattern with an area ratio of 5% were continuously printed on A4 size plain paper with an inkjet printer EM-930C. After printing, the 200th sheet of solid print image was observed with a loupe. The number of white lines or low density lines due to bending was confirmed. The results are shown in Table 1.

Claims (22)

  In an ink containing resin fine particles dyed with at least a pigment, a dispersant, water, and a fluorescent dye, the resin fine particles dyed with a fluorescent dye are emulsion polymers using at least a vinyl monomer as a raw material, The monomer is selected from a cyano group-containing vinyl monomer A, a hydroxyl group, a carboxyl group, an amino group, a carbamoyl group, a sulfonic acid group, a phosphoric acid group, and a group derived from these functional groups. A vinyl monomer obtained by mixing a vinyl monomer B having one or more groups and a vinyl monomer C other than the vinyl monomers A and B, and the vinyl monomer An ink-jet ink, wherein the monomer B is 4.75% by weight or less in the monomer mixture.   2. The ink-jet ink according to claim 1, wherein the ink liquid has a viscosity of 7.000 mPas or more.   The inkjet ink according to claim 1, comprising an alkanediol.   The inkjet ink according to claim 3, wherein the alkanediol is 2-ethyl-1.3-hexanediol.   The inkjet ink according to claim 1, wherein the resin fine particles dyed with the fluorescent dye have an average particle size of 50 to 200 nm.   The inkjet ink according to claim 1, comprising self-emulsifying polyurethane resin particles.   The inkjet ink according to claim 1, wherein an average particle size of the self-emulsifying polyurethane resin particles is 50 nm or less.   8. The ink-jet ink according to claim 1, wherein the content of the self-emulsifying polyurethane resin particles is 0.1 to 5.0% by weight.   The ink-jet ink according to any one of claims 1 to 8, wherein the pigment has an average particle diameter of 10 to 200 nm.   The inkjet ink according to claim 1, wherein the pigment is dispersed with a surfactant.   The inkjet ink according to claim 10, wherein the surfactant is a nonionic surfactant. The inkjet ink according to claim 11, wherein the surfactant is a compound represented by the following general formula (I).

(In the formula, R represents an alkyl group having 1 to 20 carbon atoms, an allyl group, or an aralkyl group, l represents an integer of 0 to 7, and n represents an integer of 20 to 200.)   The inkjet ink according to claim 12, wherein the surfactant is POE (n = 40) β-naphthyl ether.   An ink cartridge comprising the ink-jet ink according to claim 1.   The ink cartridge according to claim 14, wherein the ink cartridge is detachable from the image forming apparatus.   An image carrying medium, wherein an image formed by the ink jet ink according to claim 1 is formed on a receptor.   An image forming method comprising forming an image on a receptor using the ink jet ink according to claim 1.   The ink cartridge according to claim 15, wherein the image forming apparatus is an ink jet printer.   An image forming method, wherein an ink jet ink according to any one of claims 1 to 13 is ejected from an ink jet printer onto a receptor to form an image on the receptor.   The image forming method according to claim 19, wherein the ink jet printer is a piezo ink jet printer.   The image forming method according to claim 19, wherein the ink jet printer is a thermal ink jet printer.   The image bearing medium according to claim 16, wherein the receiver is paper.