JP6957888B2 - Ink, container and recording device - Google Patents

Description

The present invention relates to inks, storage containers and recording devices.

Inkjet recording methods have become widespread because the process is simpler and easier to full-color than other recording methods, and they are expanding from personal to office applications, commercial printing, and industrial printing. A water-based ink composition using a water-soluble dye as a coloring material is mainly used, but since it has a drawback of being inferior in water resistance and light resistance, a pigment ink using a water-insoluble pigment instead of the water-soluble dye Development is in progress.

In inkjet printing for office use, plain paper is mainly used as a recording medium, and high image density is required.
Patent Document 1 proposes an inkjet ink containing a liquid vehicle, a colorant, and a polymer having at least one functional group having a specific calcium index value.

Patent Document 2 proposes an inkjet recording method in which a receiving liquid containing a Ca salt is attached to paper, and an ink containing a pigment, a resin emulsion, and a surfactant to which a phosphorus-containing group is bonded is printed.
In Patent Document 3, an O / W emulsion of a water-insoluble (meth) acrylic resin and / or a styrene- (meth) acrylic acid copolymer having an average particle size of 50 to 200 nm and a minimum film-forming temperature of 50 ° C. or higher. , Urea or derivatives thereof, water, pigments, aqueous resins, and aqueous pigment inks comprising phosphate ester surfactants have been proposed.

Further, unlike the water-based dye ink prepared by dissolving the dye in water, the water-based pigment ink used in the above-mentioned inkjet recording method and writing utensils needs to stably disperse the pigment insoluble in water in water for a long period of time. Therefore, various pigment dispersants have been developed. For example, Patent Document 4 proposes a graft polymer containing an aromatic ring in the side chain.

However, the above-mentioned prior art has good storage stability and ejection stability, can obtain a high image density, and cannot provide an ink having good image gloss.
The present invention has been made in view of the current state of the prior art, and an object of the present invention is to provide an ink having good storage stability and ejection stability, high image density, and good image gloss. And.

The above problem is solved by the following configuration (1).
(1) An ink containing a pigment, a copolymer, and resin particles.
The pigment is contained in an amount of 7.0% by mass or more and 12% by mass or less with respect to the ink.
The content of the resin amount A in the ink is 0.5% by mass or more and 4.0% by mass or less with respect to the ink.
An ink characterized in that the 60-degree glossiness of a solid image formed by using the ink is 25% or more.

According to the present invention, it is possible to provide an ink having good storage stability and ejection stability, a high image density, and good image gloss.

It is a figure which shows an example of the ink containing container of this invention. It is explanatory drawing including the case (exterior) of the ink container example of FIG. It is a chart which shows the IR spectrum of the copolymer CP-1 obtained in Example 1. FIG. It is a chart which shows the IR spectrum of the copolymer CP-5 obtained in Example 5. It is a chart which shows the IR spectrum of the copolymer CP-7 obtained in Example 7. It is a perspective explanatory view of a recording apparatus. It is a perspective explanatory view of the main tank.

Hereinafter, the present invention will be described in detail.
The ink of the present invention contains a pigment, a copolymer, and resin particles, and contains the pigment in an amount of 7.0% by mass or more and 12% by mass or less with respect to the ink, and the amount of resin in the ink described below. The content of A is 0.5% by mass or more and 4.0% by mass or less with respect to the ink, and the 60-degree glossiness of the solid image formed by using the ink is 25% or more. And.

The ink of the present invention can obtain a high image density by increasing the amount of pigment. When the amount of pigment is increased, a large amount of copolymer for dispersing the pigment is required, but it cannot be said that the amount of the copolymer having the pigment dispersing function adsorbed on the pigment is generally high. That is, when the content of the pigment is increased, it is necessary to contain a large amount of the copolymer for dispersing the pigment, and accordingly, the abundance of the free copolymer that is not adsorbed on the pigment also increases.
On the other hand, in order to achieve the 60-degree gloss specified in the present invention, it is necessary to contain a certain amount or more of resin particles, but in such a case, the amount of copolymers and resin particles not adsorbed on the pigment increases. It adversely affects the storage stability and ejection stability of ink.
Therefore, in the present invention, by using a copolymer having a particularly high adsorption amount to the pigment, it is possible to solve the adverse effect on the ink at the same time as the high image density.
Further, by increasing the amount of the copolymer adsorbed on the pigment, the effect of improving the glossiness based on the copolymer itself can be obtained, and the synergistic effect of improving the glossiness more than simply using only the resin particles can be obtained.
Further, when plain paper is used as the recording medium, the ink of the present invention is particularly effective.

The copolymer used in the present invention (hereinafter, may be referred to as the copolymer of the present invention) preferably has a structural unit represented by the following general formulas (1) and (2).

In the general formula (1), R1 is a hydrogen atom or a methyl group, X is a hydrogen atom or a cation, and in the case of a cation, the oxygen adjacent to the cation exists as ^{O −.} As cations, sodium ion, potassium ion, lithium ion, tetramethylammonium ion, tetraethylammonium ion, tetrapropylammonium ion, tetrabutylammonium ion, tetrapentylammonium ion, tetrahexylammonium ion, triethylmethylammonium ion, tributylmethyl Ammonium ion, trioctylmethylammonium ion, 2-hydroxyethyltrimethylammonium ion, tris (2-hydroxyethyl) methylammonium ion, propyltrimethylammonium ion, hexyltrimethylammonium ion, octyltrimethylammonium ion, nonyltrimethylammonium ion, decyltrimethyl Ammonium ion, dodecyltrimethylammonium ion, tetradecyltrimethylammonium ion, hexadecyltrimethylammonium ion, octadecyltrimethylammonium ion didodecyldimethylammonium ion, ditetradecyldimethylammonium ion, dihexadecyldimethylammonium ion, dioctadecyldimethylammonium ion, Ethylhexadecyldimethylammonium ion, ammonium ion, dimethylammonium ion, trimethylammonium ion, monoethylammonium ion, diethylammonium ion, triethylammonium ion, monoethanolammonium ion, diethanolammonium ion, triethanolammonium ion, methylethanolammonium ion, Methyldiethanolammonium ion, dimethylethanolammonium ion, monopropanolammonium ion, dipropanolammonium ion, tripropanolammonium ion, isopropanolammonium ion, morpholinium ion, N-methylmorpholinium ion, N-methyl-2-pyrrolidoni Ammonium ion, 2-pyrrolidnium ion and the like can be mentioned.

In the general formula (2), R2 is a hydrogen atom or a methyl group, L is an alkylene group having 2 to 18 carbon atoms, preferably an alkylene group having 2 to 16 carbon atoms, and more preferably 2 carbon atoms. ~ 12 alkylene groups. The naphthyl group existing at the end via L has excellent pigment adsorption power due to π-π stacking with the pigment which is a coloring material in the water-based ink (hereinafter, also referred to as ink), so that it is recorded at the time of printing. By contacting the pigment on the medium, the pigment is rapidly aggregated on the surface of the recording medium, and beading (mottled) can be prevented.

As can be understood from the description of the general formulas (1) and (2), the structural unit represented by the general formulas (1) and (2) is typically a terminal naphthyl group that hangs down via L. It may be the main chain of a copolymer having a pendant group such as a side chain carboxyl group. However, of course, it does not exclude the case where a part is included in the side chain.
For example, it is a well-known fact that it is difficult to completely eliminate the secondary radical polymerization reaction that produces a branched structure.
Further, when the copolymer of the present invention is used when preparing a pigment dispersion in which a pigment is dispersed in water, a naphthyl group is present at the end of the side chain of the copolymer, so that it is easily adsorbed on the pigment surface. Since the adsorption power with the pigment is high, a highly dispersible and stable dispersion for a long period of time can be obtained.

The molar ratio of the repeating unit represented by the general formula (1) and the general formula (2) constituting the copolymer of the present invention is the general formula (1): (2) = from the viewpoint of the ability to adsorb the pigment. It is 0.1: 1 to 10: 1, preferably 0.3: 1 to 5: 1, more preferably 0.5: 1-3: 1, and particularly preferably 1: 1-3: 1. The ratio of the structural units represented by the general formula (1) to the general formula (2) is 37 to 98% by mass, preferably 54 to 95% by mass, and more preferably 66 to 92% by mass.

In the structural units represented by the general formulas (1) and (2), * represents a binding site to another structural unit.

The number average molecular weight and the weight average molecular weight of the copolymer of the present invention are preferably 500 to 10000 and 1500 to 30000, respectively, in terms of polystyrene.

The copolymer of the present invention may have a repeating unit composed of other polymerizable monomers in addition to the structural units represented by the general formulas (1) and (2).
The other polymerizable monomer is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a polymerizable hydrophobic monomer, a polymerizable hydrophilic monomer, and a polymerizable surfactant.
Examples of the polymerizable hydrophobic monomer include unsaturated ethylene monomers having an aromatic ring such as α-methylstyrene, 4-t-butylstyrene, and 4-chloromethylstyrene; methyl (meth) acrylate, (meth). ) Ethyl acrylate, -n-butyl (meth) acrylate, dimethyl maleate, dimethyl itacone, dimethyl fumarate, lauryl (meth) acrylate (C12), tridecyl (meth) acrylate (C13), (meth) Tetradecyl acrylate (C14), pentadecyl (meth) acrylate (C15), hexadecyl (meth) acrylate (C16), heptadecyl (meth) acrylate (C17), nonadecil (meth) acrylate (C19), (meth) Alkyl (meth) acrylates such as eicosyl acrylate (C20), henicosyl (meth) acrylate (C21), docosyl (meth) acrylate (C22); 1-heptene, 3,3-dimethyl-1-pentene, 4 , 4-Dimethyl-1-pentene, 3-methyl-1-hexene, 4-methyl-1-hexene, 5-methyl-1-hexene, 1-octene, 3,3-dimethyl-1-hexene, 3,4 -Dimethyl-1-hexene, 4,4-dimethyl-1-hexene, 1-nonen, 3,5,5-trimethyl-1-hexene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1 Examples thereof include unsaturated ethylene monomers having an alkyl group such as −tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene, 1-nonadecene, 1-eicosene and 1-dococene. These may be used alone or in combination of two or more.

Examples of the polymerizable hydrophilic monomer include maleic acid or a salt thereof, monomethyl maleate, itaconic acid, monomethyl itaconic acid, fumaric acid, 4-styrene sulfonic acid, 2-acrylamide-2-methylpropansulfonic acid, or Anionic unsaturated ethylene monomers such as unsaturated ethylene monomers containing phosphoric acid, phosphonic acid, alendronic acid or ethidronic acid; -2-hydroxyethyl (meth) acrylate, diethylene glycol mono (meth) acrylate, triethylene glycol mono (Meta) acrylate, tetraethylene glycol mono (meth) acrylate, polyethylene glycol mono (meth) acrylate, (meth) acrylamide, N-methylol (meth) acrylamide, N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone, Examples thereof include nonionic unsaturated ethylene monomers such as acrylamide, N, N-dimethylacrylamide, Nt-butylacrylamide, N-octylacrylamide, and Nt-octylacrylamide.
The polymerizable hydrophobic monomer and the polymerizable hydrophilic monomer are the sum of the monomers forming one or more of the polymerizable hydrophobic monomers and forming the structural unit represented by the general formula (1) and the general formula (2). It may be used in an amount of 5 to 100% by mass based on the amount.

The polymerizable surfactant is an anionic or nonionic surfactant having at least one radically polymerizable unsaturated double bond group in the molecule.
Examples of the anionic surfactant include a hydrocarbon compound having a sulfate base such as an ammonium sulfate base (-SO ₃ ^- NH ₄ ⁺ ) and an allyl group (-CH ₂ -CH = CH ₂ ), and an ammonium sulfate base (-SO _3). ^{Hydrocarbon compounds having a sulfate base such as −} NH ₄ ⁺ ) and a methacryl group [−CO−C (CH ₃ ) = CH ₂ ], or a sulfate base such as an ammonium sulfate base (−SO ₃ ⁻ NH ₄ ⁺ ) and 1 Examples thereof include aromatic hydrocarbon compounds having a −propenyl group (−CH = CH ₂ CH _3). Specific examples thereof include Eleminor JS-20 and RS-300 manufactured by Sanyo Chemical Industries, Ltd., Aqualon KH-10 manufactured by Daiichi Kogyo Seiyaku Co., Ltd., Aqualon KH-1025, Aqualon KH-05, Aqualon HS-10, and Aqualon HS. -1025, Aqualon BC-0515, Aqualon BC-10, Aqualon BC-1025, Aqualon BC-20, Aqualon BC-2020 and the like.

The nonionic surfactant is a hydrocarbon compound or aromatic having a 1-propenyl group (-CH = CH ₂ CH ₃ ) and a polyoxyethylene group [-(C ₂ H _{4 O) n-H].} Hydrocarbon compounds can be mentioned. Specific examples thereof include Aqualon RN-20, Aqualon RN-2025, Aqualon RN-30, and Aqualon RN-50 manufactured by Dai-ichi Kogyo Seiyaku Co., Ltd., Latemul PD-104, Latemul PD-420, and Latemul PD manufactured by Kao Corporation. -430, Latemul PD-450 and the like.

The polymerizable surfactant is 0.1 to 10% by mass based on the monomer obtained by mixing one or more of them to form the structural unit represented by the general formula (1) and the general formula (2). You can use it.

In the copolymer of the present invention, as shown in the following reaction formulas (1) to (3), first, naphthalenecarbonyl chloride (A-1) and an excess amount of a diol compound are added to an acid acceptor such as amine or pyridine. Condensation reaction in the presence gives naphthalenecarboxylic acid hydroxyalkyl ester (A-2). Next, 2-methacryloyloxyethyl isocyanate (A-3) was reacted with the above (A-2) to obtain a monomer (A-4), and then a (meth) acrylic acid monomer in the presence of a radical polymerization initiator. By copolymerizing with (A-5), the copolymer (A-6) of the present invention can be obtained. Here, the weight average molecular weight of the monomer (A-4) is 357 to 596 because L in the general formula (2) is an alkylene group having 2 to 18 carbon atoms and R2 is a hydrogen atom or a methyl group. ..

The radical polymerization initiator is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include peroxyketal, hydroperoxide, dialkyl peroxide, diacyl peroxide, peroxydicarbonate, peroxyester, cyano-based azobisisobutyronitrile, and azobis (2-methylbutyronitrile). Examples thereof include azobis (2,2'-isovaleronitrile) and non-cyano dimethyl-2,2'-azobisisobutyrate. Among these, organic peroxides and azo compounds are preferable, and azo compounds are particularly preferable, because the molecular weight can be easily controlled and the decomposition temperature is low.

The content of the radical polymerization initiator is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 1 to 10% by mass with respect to the total amount of the polymerizable monomer.

In order to adjust the molecular weight of the copolymer of the present invention, an appropriate amount of the chain transfer agent may be added.
Examples of the chain transfer agent include mercaptoacetic acid, mercaptopropionic acid, 2-propanethiol, 2-mercaptoethanol, thiophenol, dodecyl mercaptan, 1-dodecanethiol, thioglycerol, and the like.
The polymerization temperature is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 50 ° C. to 150 ° C., more preferably 60 ° C. to 100 ° C. The polymerization time is also not particularly limited and may be appropriately selected depending on the intended purpose, but 3 to 48 hours is preferable.

The content of the copolymer of the present invention in the ink is preferably 1.0 to 3.5% by mass, more preferably 1.5 to 3.0% by mass, from the viewpoint of enhancing the effect of the present invention.

It is particularly preferable to use carbon black as the pigment used in the present invention, and for example, carbon black produced by a known method such as a contact method, a furnace method, or a thermal method can be used.
Examples of black pigments include carbon black (CI pigment black 7) such as furnace black, lamp black, acetylene black, and channel black, and metals such as copper and iron (CI pigment black 11). Examples thereof include metal oxides such as titanium oxide and organic pigments such as aniline black (CI pigment black 1).
The carbon black is a carbon black produced by the furnace method or the channel method, having a primary particle size of 15 to 40 nm, a specific surface area of 50 to 300 m ² / g by the BET method, and a DBP oil absorption of 40 to 150 mL / 100 g. Those having a volatile content of 0.5 to 10% and a pH of 2 to 9 are preferable.
Among these pigments, those having a good affinity for water are particularly preferably used.

In addition, pigments other than carbon black can be used in the ink of the present invention as needed.

The content of the pigment in the ink can be appropriately selected, but is required to be 7.0 to 12% by mass, more preferably 8.0 to 10% by mass.
If it is less than 7.0% by mass, a high image density cannot be obtained. Further, if it exceeds 12.0 mass, the discharge stability and the storage stability deteriorate.

The content of water in the ink used in the present invention is not particularly limited and may be appropriately selected depending on the intended purpose. However, from the viewpoint of ink drying property and ejection reliability, 10% by mass or more and 90% by mass or less is used. It is preferably 20% by mass to 60% by mass, more preferably.

The resin particles used in the present invention preferably have an average volume particle size (D50) of 500 nm or less, more preferably 80 to 250 nm, and particularly preferably 100 to 220 nm. Specific examples of the resin particles include a condensation-based synthetic resin, an addition-based synthetic resin, and a natural polymer compound.
Examples of the condensed synthetic resin include polyester resin, polyurethane resin, polyepoxy resin, polyamide resin, polyether resin, poly (meth) acrylic resin, acrylic-silicone resin, and fluororesin. Examples of the additive synthetic resin include polyolefin resins, polystyrene resins, polyvinyl alcohol resins, polyvinyl ester resins, polyacrylic acid resins, unsaturated carboxylic acid resins and the like. Examples of the natural polymer compound include celluloses, rosins, and natural rubbers.
Of these, polyurethane resin, acrylic-silicone resin, and acrylic-styrene resin are particularly preferable.

When the volume average particle diameter (D50) of the resin particles is 80 nm or more and 250 nm or less, the image uniformity is improved. It is considered that this is because it is possible to prevent uneven aggregation of pigment particles in the process of drying the ink on the recording medium. When the volume average particle size is several tens of μm, it becomes larger than the nozzle opening of the inkjet head and cannot be used. If particles with a large particle size are present in the ink even if they are smaller than the nozzle opening, the ejection stability is deteriorated. Therefore, the volume average particle size (D50) is preferably 500 nm or less so as not to impair the ink ejection stability.
Here, the volume average particle diameter (D50) of the resin particles was measured by a dynamic light scattering method with a Microtrack UPA manufactured by Nikkiso Co., Ltd. in an environment of 23 ° C. and 55% RH.

The content of the resin particles in the ink is preferably 0.5 to 15% by mass, more preferably 0.5 to 8% by mass, and particularly preferably 1 to 3% by mass in terms of solid content.
Further, the resin particles may have a function of fixing the pigment on the paper surface. In that case, the minimum film-forming temperature (MFT) of the resin particles is preferably 30 ° C. or lower in order to form a film at room temperature to improve the fixability of the coloring material.
Further, depending on the glass transition temperature of the resin particles, the viscosity of the resin film may become strong and the printed matter may be tacked. When the glass transition temperature of the resin particles is −40 ° C. or lower, the viscosity becomes high, so it is advantageous that the glass transition temperature is −30 ° C. or higher.
Further, as the resin particles, a plurality of resin particles are used in consideration of film forming property (image forming property), high water repellency, high water resistance, high weather resistance, high water resistance and high image density (high color development). It doesn't matter.

In the ink of the present invention, the amount of resin A quantified by the following method is 0.5% by mass or more and 4.0% by mass or less with respect to the total amount of ink.
The amount of resin A is more preferably 0.5% by mass to 3.5% by mass with respect to the total amount of ink. If it is less than 0.5% by mass, the storage stability is inferior, and if it exceeds 4.0% by mass, the glossiness, the storage stability and the ejection property are inferior.

<Method for quantifying the amount of resin A>
The amount of resin A in the ink is determined as follows.
1 g of ink is centrifuged at 15,000 rpm for 1 hour using an ultracentrifugation device CP100MX (manufactured by Hitachi, Ltd.) in an environment of 25 ° C. to precipitate the pigment and recover the supernatant. The mass of the supernatant liquid recovered at this time is defined as the amount of the supernatant liquid B (g) in 1 g of the ink. The supernatant is subjected to thermogravimetric analysis using DTG60 (manufactured by Shimadzu Corporation) as follows. 50 mg of the supernatant is placed on the platinum cell, the temperature is raised from 30 ° C. to 120 ° C. at a rate of temperature rise of 10 ° C./min under a nitrogen atmosphere, the temperature is maintained at 120 ° C. for 20 minutes, and the temperature is further raised to 800 ° C. The mass difference between the mass after holding at 120 ° C. and the mass at the time of raising the temperature at 800 ° C. is the amount of resin contained in 50 mg of the supernatant liquid.
The value of the resin amount A in the ink can be obtained by the following calculation formula.
Amount of resin A (g) = Amount of resin in 1 g of ink A * Ink mass (g) = {{(mass g after holding at 120 ° C.)-(mass g at 800 ° C. temperature rise)} / 0.050 g} * B * Ink mass (g)
B: Amount of supernatant liquid (g) in 1 g of ink
The content of the resin amount A in the ink can be calculated from the resin amount A (g) obtained from the above calculation formula and the mass of the ink.

The 60-degree glossiness of the image formed by using the ink of the present invention needs to be 25% or more, more preferably 51% or less. If it is less than 25%, the image on the coated paper becomes matte and the sense of quality is inferior. If it exceeds 51%, the image will shine and become difficult to see.

<Measurement method of 60 degree glossiness>
Inkjet printer (Ricoh Co., Ltd., IPSIO GX5000) was filled with ink under a 50% RH environment at 23 ° C, and then a recording medium for gloss recording (Ricoh Business Coat Gloss 100, background 60 degrees gloss: 21%, A solid image (length 50 mm, width 180 mm) with a resolution of 1,200 dpi is printed on Ricoh Corporation. Then, the solid image is dried for 120 seconds in a constant temperature bath set so that the internal temperature is 100 ° C. Next, the 60-degree glossiness of the solid image is measured using a glossiness meter (Micro-Gloss 60 ° manufactured by Atlas). As for the print mode, use the "glossy paper-clean" mode from the user setting of glossy paper with the driver attached to the printer.

In the present invention, the mass ratio of the resin amount A in the ink to the pigment in the ink is preferably 5% or more and 50% or less, and more preferably 10% or more and 45% or less. When the mass ratio is 5% or more, storage stability is excellent, and when it is 50% or less, discharge stability and glossiness are excellent.

The water-based ink of the present invention is water-soluble in order to enhance the permeability to plain paper, coated paper, etc., further suppress the occurrence of beading, and to prevent the ink from drying by utilizing the wetting effect. It is preferable to use an organic solvent such as an organic solvent.
The water-soluble organic solvent is not particularly limited, and for example, ethylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, polyethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, polypropylene glycol, 1,3-butanediol. , 3-Methyl-1,3-butanediol, trimethylolethane, trimethylolpropane, 1,5-pentanediol, 1,6-hexanediol, hexylene glycol, glycerin, 1,2,3-butanetriol, 1 , 2,4-Butantriol, 1,2,6-hexanetriol, isopropylideneglycerol, petriol and other polyhydric alcohols; ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, Polyhydric alcohol alkyl ethers such as diethylene glycol monobutyl ether, tetraethylene glycol monomethyl ether, propylene glycol monoethyl ether; polyhydric alcohol aryl ethers such as ethylene glycol monophenyl ether and ethylene glycol monobenzyl ether; 2-pyrrolidone, N- Nitrogen-containing heterocyclic compounds such as methyl-2-pyrrolidone, N-hydroxyethyl-2-pyrrolidone, 1,3-dimethylimidazolidinone, ε-caprolactam, γ-butyrolactone; formamide, N-methylformamide, N, N Amidos such as −dimethylformamide, 3-methoxy-N, N-dimethylpropionamide, 3-butoxy-N, N-dimethylpropionamide; monoethanolamine, diethanolamine, triethanolamine, monoethylamine, diethylamine, triethylamine, etc. Amines; sulfur-containing compounds such as dimethylsulfoxide, sulfolane, thiodiethanol; 3-ethyl-3-hydroxymethyloxetane, propylene carbonate, ethylene carbonate and the like can be mentioned. These may be used alone or in combination of two or more.
Among these, 3-ethyl-3-hydroxymethyloxetane, isopropylideneglycerol, N, N-dimethyl-β-methoxypropionamide, N, N-dimethyl-β-butoxypropionamide, from the viewpoint of curl prevention in plain paper. Is preferable.
Further, diethylene glycol, triethylene glycol, 1,3-butanediol, 2,2,4-trimethyl-1,3-pentanediol and glycerin are excellent in preventing discharge defects due to water evaporation.

Further, as an organic solvent which is sparingly soluble in water, has relatively low wettability, and has permeability, for example, 2-ethyl-1,3-hexanediol [solubility in water: 4.2% (25 ° C.). )], 2,2,4-trimethyl-1,3-pentanediol [solubility in water: 2.0% (25 ° C.)], and the like.

Organic solvents other than the above include 2-ethyl-2-methyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, and 2-methyl-2-propyl-1 as aliphatic diols. , 3-Propanediol, 3,3-dimethyl-1,2-butanediol, 2,4-dimethyl-2,4-pentanediol, 2,5-dimethyl-2,5-hexanediol, 5-hexene-1 , 2-diol and the like can be used.

Further, examples of the water-soluble organic solvent that can be used in combination with the above-mentioned water-soluble organic solvent include alkyl and aryl ethers of polyhydric alcohols such as propylene glycol monobutyl ether, diethylene glycol monophenyl ether, ethylene glycol monoallyl ether, and tetraethylene glycol chlorophenyl ether. , Lower alcohols such as ethanol can be appropriately selected and used according to the purpose.

The content of the organic solvent in the ink is preferably 15 to 70% by mass, more preferably 20 to 60% by mass, from the viewpoint of enhancing the effect of the present invention.

In the water-based ink of the present invention, it is preferable to use a surfactant in order to enhance the permeability and wettability to plain paper, coated paper and the like, and further suppress the occurrence of beading.
As the surfactant, for example, a fluorine-based surfactant, a silicone-based surfactant, an anionic surfactant, a nonionic surfactant, and a betaine-based surfactant can be used. These surfactants may be used alone or in combination of two or more.
Among these, fluorine-based surfactants and silicone-based surfactants are preferable because the surface tension can be reduced to 30 mN / m or less.

Examples of the fluorine-based surfactant include nonionic fluorine-based surfactants, anionic fluorine-based surfactants, amphoteric fluorine-based surfactants, and oligomer-type fluorine-based surfactants. Further, those having a fluorine-substituted carbon number of 2 to 16 are preferable, and those having a fluorine-substituted carbon number of 4 to 16 are more preferable. If the number of carbon atoms is less than 2, the effect peculiar to the fluorine-based surfactant may not be obtained, and if it exceeds 16, problems such as storage stability may occur.
Examples of the nonionic fluorine-based surfactant include a perfluoroalkyl phosphate ester compound, a perfluoroalkylethylene oxide adduct, and a polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in the side chain. Among these, a polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in the side chain is preferable because it has low foaming property, and a fluorine-based surfactant represented by the following general formula (5) is more preferable.
CF ₃ CF ₂ (CF ₂ CF ₂ ) m-CF ₂ CF ₂ (CF ₂ CF ₂ ) nH ・ ・ ・ General formula (5)
(In the formula, m is 0 to 10, n is 0 to 40)

Examples of the anionic fluorine-based surfactant include a perfluoroalkyl sulfonic acid compound, a perfluoroalkyl carboxylic acid compound, a perfluoroalkyl phosphate ester compound, and a polyoxyalkylene ether polymer having a perfluoroalkyl ether group in the side chain. Examples include compounds.
Examples of the perfluoroalkyl sulfonic acid compound include perfluoroalkyl sulfonic acid and perfluoroalkyl sulfonic acid salt.
Examples of the perfluoroalkylcarboxylic acid compound include perfluoroalkylcarboxylic acid and perfluoroalkylcarboxylic acid salt.
Examples of the perfluoroalkyl phosphate ester compound include a perfluoroalkyl phosphate ester and a salt of a perfluoroalkyl phosphate ester.
Examples of the polyoxyalkylene ether polymer compound having a perfluoroalkyl ether group in the side chain include a polyoxyalkylene ether polymer having a perfluoroalkyl ether group in the side chain and a polyoxyalkylene ether having a perfluoroalkyl ether group in the side chain. Examples thereof include a sulfate ester salt of the polymer and a salt of a polyoxyalkylene ether polymer having a perfluoroalkyl ether group in the side chain.
The counter ions of the salts in these fluorine-based surfactants are Li, Na, K, NH ₄ , NH ₃ CH ₂ CH ₂ OH, NH ₂ (CH ₂ CH ₂ OH) ₂ , NH (CH ₂ CH ₂ OH). ) ₃ and so on.

Commercially available fluorine-based surfactants include, for example, Surflon S-111, S-112, S-113, S-121, S-131, S-132, S-141, and S-145 (all from Asahi Glass Co., Ltd.). (Manufactured by); Fullrad FC-93, FC-95, FC-98, FC-129, FC-135, FC-170C, FC-430, FC-431 (all manufactured by Sumitomo 3M); Megafuck F-470 , F-1405, F-474 (all manufactured by Dainippon Ink and Chemicals Co., Ltd.); Zonyl TBS, FSP, FSA, FSN-100, FSN, FSO-100, FSO, FS-300, UR (all Also manufactured by DuPont); Surfactant FT-110, FT-250, FT-251, FT-400S, FT-150, FT-400SW (all manufactured by Neos), Polyfox PF-136A, PF-156A , PF-151N, PF-154, PF-159 (manufactured by Omniova) and the like.
Among these, FS-300 manufactured by DuPont, FT-110, FT-250, FT-251 and FT- of Neos are significantly improved in good print quality, especially color development and leveling property on paper. 400S, FT-150, FT-400SW, and Polyfox PF-151N manufactured by Omniova are particularly preferable.

The silicone-based surfactant is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include side chain modified polydimethylsiloxane, double-ended modified polydimethylsiloxane, single-ended modified polydimethylsiloxane, side chain double-ended modified polydimethylsiloxane, and examples thereof include polyoxyethylene group and polyoxyethylene. A polyether-modified silicone-based surfactant having a polyoxypropylene group is particularly preferable because it exhibits good properties as an aqueous surfactant.
Commercially available silicone-based surfactants can be easily obtained from, for example, Big Chemie, Shin-Etsu Chemical, Toray Dow Corning Silicone, Nippon Emulsion, Kyoei Kagaku, and the like.

Examples of the anionic surfactant include salts of polyoxyethylene alkyl ether acetate, dodecylbenzene sulfonate, lauryl salt, and polyoxyethylene alkyl ether sulfate.
Examples of the nonionic surfactant include polyoxyethylene alkyl ether, polyoxypropylene alkyl ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl amine, and poly. Examples thereof include oxyethylene alkyl amide.

To the ink of the present invention, as other components, a pH adjuster, an antiseptic antifungal agent, a rust preventive agent, an antioxidant, an ultraviolet absorber, an oxygen absorber, a light stabilizer and the like are appropriately added as necessary. can do.
The pH adjuster is not particularly limited as long as it can adjust the pH to 8.5 to 11 without adversely affecting the ink to be blended, and can be appropriately selected depending on the intended purpose. Examples thereof include alcohol amines, alkali metal element hydroxides, ammonium hydroxides, phosphonium hydroxides, alkali metal carbonates, and the like. Examples of the alcohol amines include diethanolamine, triethanolamine, 2-amino-2-ethyl-1,3-propanediol, and the like. Examples of the hydroxide of the alkali metal element include lithium hydroxide, sodium hydroxide, potassium hydroxide and the like. Examples of the ammonium hydroxide include ammonium hydroxide and quaternary ammonium hydroxide. Examples of the phosphonium hydroxide include a quaternary phosphonium hydroxide. Examples of the alkali metal carbonate include lithium carbonate, sodium carbonate, potassium carbonate and the like.

Examples of the antiseptic and antifungal agent include sodium dehydroacetate, sodium sorbate, sodium 2-pyridinethiol-1-oxide, sodium benzoate, sodium pentachlorophenol and the like.

Examples of the rust preventive include acidic sulfite, sodium thiosulfate, ammon 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.

Examples of the ultraviolet absorber include benzophenone-based ultraviolet absorbers, benzotriazole-based ultraviolet absorbers, salicylate-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, nickel complex salt-based ultraviolet absorbers, and the like.

The ink of the present invention is produced, for example, by dispersing or dissolving the pigment, water, the organic solvent, the copolymer, the resin particles, and if necessary, other components in an aqueous medium, and stirring and mixing them. be able to. Further, the copolymer may be used as a pigment dispersion resin when producing a pigment dispersion.
The dispersion can be performed by, for example, a sand mill, a homogenizer, a ball mill, a paint shaker, an ultrasonic disperser, etc., and stirring and mixing are performed by a stirrer using ordinary stirring blades, a magnetic stirrer, a high-speed disperser, or the like. be able to.

In the production, it is preferable to filter the coarse particles with a filter, a centrifuge, or the like, if necessary, and degas.

The physical characteristics of the ink of the present invention are not particularly limited and may be appropriately selected depending on the intended purpose. For example, the viscosity, surface tension and the like are preferably in the following ranges.
The viscosity of the ink at 25 ° C. is preferably 3 to 20 mPa · s. When the viscosity is 3 mPa · s or more, the effect of improving the print density and the character quality can be obtained. Further, by setting the value to 20 mPa · s or less, the ink ejection property can be ensured.
The viscosity can be measured at 25 ° C. using, for example, a viscometer (RE80L, manufactured by Toki Sangyo Co., Ltd.).

The surface tension of the ink is preferably 40 mN / m or less at 25 ° C.

The ink container of the present invention contains the ink in the container and further has other members appropriately selected as needed.
The container is not particularly limited, and its shape, structure, size, material, etc. can be appropriately selected according to the purpose. For example, it has at least an ink bag made of an aluminum laminate film, a resin film, or the like. Things, etc. are suitable.

The ink container will be described with reference to FIGS. 1 and 2.
FIG. 1 is a diagram showing an example of an ink container, and FIG. 2 is a diagram including a case (exterior) of the ink container of FIG. The ink container 200 fills the ink bag 241 with ink from the ink injection port 242, exhausts the ink, and then closes the ink injection port 242 by fusion.
At the time of use, the needle of the main body of the device is pierced into the ink discharge port 243 made of a rubber member to supply the ink to the device. The ink bag 241 is formed of a packaging member such as a non-permeable aluminum laminated film. As shown in FIG. 2, the ink bag 241 is usually housed in a plastic storage container case 244, and is detachably attached to various inkjet recording devices for use.

The ink of the present invention can be suitably used for various recording devices by an inkjet recording method, for example, a printer, a facsimile device, a copying device, a printer / fax / copier multifunction device, a three-dimensional modeling device, and the like.
In the present invention, the recording device and the recording method are devices capable of ejecting ink, various processing liquids, and the like to a recording medium, and a method of recording using the device. The recording medium means a medium to which ink and various treatment liquids can adhere even temporarily.
This recording device can include not only a head portion for ejecting ink, but also means related to feeding, transporting, and discharging paper of a recording medium, and other devices called pretreatment devices and posttreatment devices. ..
The recording device and recording method may include a heating means used in the heating step and a drying means used in the drying step. The heating means and the drying means include, for example, means for heating and drying the print surface and the back surface of the recording medium. The heating means and the drying means are not particularly limited, but for example, a hot air heater and an infrared heater can be used. Heating and drying can be performed before printing, during printing, after printing, and the like.
Further, the recording device and the recording method are not limited to those in which significant images such as characters and figures are visualized by ink. For example, those that form patterns such as geometric patterns and those that form a three-dimensional image are also included.
Further, the recording device includes both a serial type device that moves the discharge head and a line type device that does not move the discharge head, unless otherwise specified.
Further, as this recording device, it is possible to use not only a desktop type but also a wide recording device capable of printing on an A0 size recording medium, or, for example, continuous paper wound in a roll shape as a recording medium. A continuous line printer is also included.
An example of the recording device will be described with reference to FIGS. 6 to 7. FIG. 6 is a perspective explanatory view of the device. FIG. 7 is a perspective explanatory view of the main tank. The image forming apparatus 400 as an example of the recording apparatus is a serial type image forming apparatus. A mechanism portion 420 is provided in the exterior 401 of the image forming apparatus 400. Each ink storage section 411 of the main tank 410 (410k, 410c, 410m, 410y) for each color of black (K), cyan (C), magenta (M), and yellow (Y) is, for example, a package of an aluminum laminated film or the like. It is formed of members. The ink container 411 is housed in, for example, a plastic container case 414. As a result, the main tank 410 is used as an ink cartridge for each color.
On the other hand, a cartridge holder 404 is provided behind the opening when the cover 401c of the apparatus main body is opened. The main tank 410 is detachably attached to the cartridge holder 404. As a result, each ink discharge port 413 of the main tank 410 and the discharge head 434 for each color communicate with each other via the supply tube 436 for each color, and ink can be discharged from the discharge head 434 to the recording medium.

As the recording medium, plain paper is preferable, but in addition, glossy paper, special paper, cloth, film, OHP sheet, general-purpose printing paper and the like can be used.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples. In addition, "part" and "%" in an example are "part by weight" and "mass%" unless otherwise specified.
The molecular weights of the copolymers obtained in Examples and Comparative Examples were determined as follows.

<Measurement of molecular weight of copolymer>
It was measured by GPC (Gel Permeation Chromatography) under the following conditions.
・ Equipment: GPC-8020 (manufactured by Tosoh Corporation)
-Column: TSK G2000HXL and G4000HXL (manufactured by Tosoh Corporation)
・ Temperature: 40 ℃
-Solvent: THF (tetrahydrofuran)
-Flow velocity: 1.0 mL / min Inject 1 mL of a copolymer with a concentration of 0.5% by mass, and use a molecular weight calibration curve prepared from a monodisperse polystyrene standard sample from the molecular weight distribution of the copolymer measured under the above conditions. The number average molecular weight Mn and the weight average molecular weight Mw of the copolymer were calculated.

[Example 1: Synthesis of copolymer CP-1]
62.0 g (525 mmol) of 1,6-hexanediol (manufactured by Tokyo Kasei Co., Ltd.) was dissolved in 700 mL of methylene chloride, and 20.7 g (262 mmol) of pyridine was added.
A solution prepared by dissolving 50.0 g (262 mmol) of 2-naphthalenecarbonyl chloride (manufactured by Tokyo Kasei Co., Ltd.) in 100 mL of methylene chloride was added dropwise to this solution with stirring over 2 hours, and then the mixture was stirred at room temperature for 6 hours. .. After washing the obtained reaction solution with water, the organic phase was isolated, dried over magnesium sulfate, and the solvent was distilled off. The residue was purified by silica gel column chromatography using a mixed solvent of methylene chloride / methanol (volume ratio 98/2) as an eluent to obtain 52.5 g of 2-naphthoic acid-2-hydroxyethyl ester.

Next, 42.1 g (155 mmol) of 2-naphthoic acid-2-hydroxyethyl ester was dissolved in 80 mL of dry methyl ethyl ketone and heated to 60 ° C. A solution prepared by dissolving 24.0 g (155 mmol) of 2-methacryloyloxyethyl isocyanate (Carens MOI, manufactured by Showa Denko KK) in 20 mL of dry methyl ethyl ketone was added dropwise to this solution with stirring over 1 hour, and then at 70 ° C. Was stirred for 12 hours. After cooling to room temperature, the solvent was distilled off. The residue was purified by silica gel column chromatography using a mixed solvent of methylene chloride / methanol (volume ratio 99/1) as an eluent to obtain 57.0 g of the structure represented by the following structural formula (4-1). The monomer M-1 having was obtained.

Next, 1.20 g (16.7 mmol) of acrylic acid (manufactured by Aldrich) and 7.12 g (16.7 mmol) of monomer M-1 were dissolved in 40 mL of dry methyl ethyl ketone to prepare a monomer solution. A solution in which 0.273 g (1.67 mmol) of 2,2'-azoiso (butyronitrile) (manufactured by Tokyo Kasei Co., Ltd.) is dissolved in the remaining monomer solution after heating 10% of the monomer solution to 75 ° C. under an argon air stream. Was added dropwise over 1.5 hours, and the mixture was stirred at 75 ° C. for 6 hours. After cooling to room temperature, the obtained reaction solution was dropped into hexane. The precipitated copolymer was filtered off and dried under reduced pressure to obtain 8.13 g of the copolymer CP-1 (weight average molecular weight (Mw): 9200, number average molecular weight (Mn): 3100). The IR spectrum of the obtained copolymer is shown in FIG.

Next, the obtained 2.00 g of the copolymer was dissolved in an aqueous solution of tetraethylammonium (TEA) hydroxide so that the concentration of the copolymer was 11.9% and the pH was 8.0, and the copolymer was used. An aqueous solution for pigment dispersion of the polymer CP-1 was prepared.

[Example 2: Synthesis of copolymer CP-2]
Monomer M- having a structure represented by the following structural formula (4-2) in the same manner as in Example 1 except that ethylene glycol (manufactured by Tokyo Kasei Co., Ltd.) was used instead of 1,6-hexanediol. I got 2.

Next, using acrylic acid and the obtained monomer M-2, a copolymer (weight average molecular weight (Mw): 8700, number average molecular weight (Mn): 3000) was obtained in the same manner as in Example 1. , An aqueous solution for pigment dispersion of the copolymer CP-2 was prepared in the same manner as in Example 1. The IR spectrum of the obtained copolymer CP-2 showed the same IR spectrum as that of the copolymer CP-1.

[Example 3: Synthesis of copolymer CP-3]
The structure represented by the following structural formula (4-3) is the same as in Example 1 except that 1,12-dodecanediol (manufactured by Tokyo Kasei Co., Ltd.) is used instead of 1,6-hexanediol. The monomer M-3 having was obtained.

Next, using acrylic acid and the obtained monomer M-3, a copolymer (weight average molecular weight (Mw): 8700, number average molecular weight (Mn): 3000) was obtained in the same manner as in Example 1. , An aqueous solution for pigment dispersion of the copolymer CP-3 was prepared in the same manner as in Example 1. The IR spectrum of the obtained copolymer CP-3 showed the same IR spectrum as that of the copolymer CP-1.

[Example 4: Synthesis of copolymer CP-4]
It has a structure represented by the following formula (4-4) in the same manner as in Example 1 except that 1,16-hexadecanediol (manufactured by Tokyo Kasei Co., Ltd.) is used instead of 1,6-hexanediol. Monomer M-4 was obtained.

Next, using acrylic acid and the obtained monomer M-4, a copolymer (weight average molecular weight (Mw): 9400, number average molecular weight (Mn): 3400) was obtained in the same manner as in Example 1. , An aqueous solution for pigment dispersion of the copolymer CP-4 was prepared in the same manner as in Example 1. The IR spectrum of the obtained copolymer CP-4 showed the same IR spectrum as that of the copolymer CP-1.

[Example 5: Synthesis of copolymer CP-5]
Using methacrylic acid and the monomer M-1 synthesized in Example 1, a copolymer (weight average molecular weight (Mw): 9300, number average molecular weight (Mn): 3300) was obtained in the same manner as in Example 1. , An aqueous solution of the copolymer CP-5 was prepared in the same manner as in Example 1. FIG. 4 shows the IR spectrum of the obtained copolymer CP-5.

[Example 6: Synthesis of copolymer CP-6]
Acrylic acid and the monomer M-1 synthesized in Example 1 were changed to the ratios shown in Table 1 and used, and the copolymer (weight average molecular weight (Mw): 9100, number average molecular weight) was used in the same manner as in Example 1. (Mn): 3100) was obtained, and an aqueous solution for pigment dispersion of the copolymer CP-6 was prepared in the same manner as in Example 1. The IR spectrum of the obtained copolymer CP-6 showed the same IR spectrum as that of the copolymer CP-1.

[Example 7: Synthesis of copolymer CP-7]
Acrylic acid and the monomer M-1 synthesized in Example 1 were changed to the ratios shown in Table 1 and used, and the copolymer (weight average molecular weight (Mw): 8700, number average molecular weight) was used in the same manner as in Example 1. (Mn): 2900) was obtained, and an aqueous solution for pigment dispersion of the copolymer CP-7 was prepared in the same manner as in Example 1. FIG. 5 shows the IR spectrum of the obtained copolymer CP-7.

[Example 8: Synthesis of copolymer CP-8]
Acrylic acid and the monomer M-1 synthesized in Example 1 were changed to the ratios shown in Table 1 and used in the same manner as in Example 1 to obtain a copolymer (weight average molecular weight (Mw): 8500, number average molecular weight (number average molecular weight). Mn): 2800) was obtained, and an aqueous solution for pigment dispersion of the copolymer CP-8 was prepared in the same manner as in Example 1. The IR spectrum of the obtained copolymer CP-8 showed the same IR spectrum as that of the copolymer CP-7.

[Example 9: Synthesis of copolymer CP-9]
Using acrylic acid and the monomer M-1 synthesized in Example 1, a copolymer (weight average molecular weight (Mw): 8600, number average molecular weight (Mn): 3000) was obtained in the same manner as in Example 1. .. The obtained 2.00 g of the copolymer was dissolved in an aqueous sodium hydroxide solution so that the concentration of the copolymer was 11.9% and the pH was 8.0 to obtain the copolymer CP-9. An aqueous solution for pigment dispersion was prepared. The IR spectrum of the obtained copolymer CP-9 showed the same IR spectrum as that of the copolymer CP-1.

[Example 10: Synthesis of copolymer CP-10]
Methacrylic acid and the monomer M-4 synthesized in Example 4 were changed to the ratios shown in Table 1 and used in the same manner as in Example 1 to obtain a copolymer (weight average molecular weight (Mw): 9400, number average molecular weight (number average molecular weight). Mn): 3600) was obtained, and an aqueous solution for pigment dispersion of the copolymer CP-10 was prepared in the same manner as in Example 9. The IR spectrum of the obtained copolymer CP-10 showed the same IR spectrum as that of the copolymer CP-5.

[Example 11; Preparation of water-based ink GJ-1]
(Preparation of pigment dispersion PD-1)
To 44.1 parts of the copolymer CP-1 aqueous solution prepared in Example 1, 21.0 parts of carbon black (NIPEX150, manufactured by Degussa) and 34.0 parts of ion-exchanged water were added and stirred for 12 hours. .. The obtained mixture was circulated and dispersed at a peripheral speed of 10 m / s for 1 hour using a disc-type bead mill (manufactured by Simmal Enterprises, KDL type, media: using zirconia balls having a diameter of 0.1 mm), and then the pore diameter was 1. The mixture was filtered through a 2 μm membrane filter, and an adjusted amount of ion-exchanged water was added to obtain 100.0 parts of a pigment dispersion PD-1 (pigment solid content concentration: 21%).

(Making ink)
45.0 parts of pigment dispersion PD-1, 10.0 parts of 1,3-butanediol, 10.0 parts of glycerin, 10.0 parts of 3-methoxy-N, N-dimethylpropionamide, 1. 0 parts of Zonir FS-300 (Dupont, fluorine-based surfactant, solid content 40% by mass), urethane resin emulsion UA-368T (Sanyo Kasei Co., Ltd., solid content mass 50%)) 6.0 parts, And 18.0 parts of ion-exchanged water were mixed, stirred for 1 hour, and then filtered through a membrane filter having a pore size of 1.2 μm to obtain the water-based ink GJ-1 of the present invention.

[Example 12; Preparation of water-based ink GJ-2]
A pigment dispersion PD-2 was obtained in the same manner except that an aqueous solution of the copolymer CP-2 was used instead of the aqueous solution of the copolymer CP-1 in the preparation of the pigment dispersion of Example 11.
Next, the water-based ink GJ-2 of the present invention was obtained in the same manner except that the pigment dispersion PD-2 was used instead of the pigment dispersion PD-1 in the preparation of the ink of Example 11.

[Example 13; Preparation of water-based ink GJ-3]
The pigment dispersion PD-3 was obtained in the same manner except that the aqueous solution of the copolymer CP-3 was used instead of the aqueous solution of the copolymer CP-1 in the preparation of the pigment dispersion of Example 11.
Next, the water-based ink GJ-3 of the present invention was obtained in the same manner except that the pigment dispersion PD-3 was used instead of the pigment dispersion PD-1 in the preparation of the ink of Example 11.

[Example 14; Preparation of water-based ink GJ-4]
The pigment dispersion PD-4 was obtained in the same manner except that the aqueous solution of the copolymer CP-4 was used instead of the aqueous solution of the copolymer CP-1 in the preparation of the pigment dispersion of Example 11.
Next, the water-based ink GJ-4 of the present invention was obtained in the same manner except that the pigment dispersion PD-4 was used instead of the pigment dispersion PD-1 in the preparation of the ink of Example 11.

[Example 15; Preparation of water-based ink GJ-5]
A pigment dispersion PD-5 was obtained in the same manner except that an aqueous solution of the copolymer CP-5 was used instead of the aqueous solution of the copolymer CP-1 in the preparation of the pigment dispersion of Example 11.
Next, the water-based ink GJ-5 of the present invention was obtained in the same manner except that the pigment dispersion PD-5 was used instead of the pigment dispersion PD-1 in the preparation of the ink of Example 11.

[Example 16; Preparation of water-based ink GJ-6]
A pigment dispersion PD-6 was obtained in the same manner except that an aqueous solution of the copolymer CP-6 was used instead of the aqueous solution of the copolymer CP-1 in the preparation of the pigment dispersion of Example 11.
Next, the water-based ink GJ-6 of the present invention was obtained in the same manner except that the pigment dispersion PD-6 was used instead of the pigment dispersion PD-1 in the preparation of the ink of Example 11.

[Example 17; Preparation of water-based ink GJ-7]
A pigment dispersion PD-7 was obtained in the same manner except that an aqueous solution of the copolymer CP-7 was used instead of the aqueous solution of the copolymer CP-1 in the preparation of the pigment dispersion of Example 11.
Next, the water-based ink GJ-7 of the present invention was obtained in the same manner except that the pigment dispersion PD-7 was used instead of the pigment dispersion PD-1 in the preparation of the ink of Example 11.

[Example 18; Preparation of water-based ink GJ-8]
A pigment dispersion PD-8 was obtained in the same manner except that an aqueous solution of the copolymer CP-8 was used instead of the aqueous solution of the copolymer CP-1 in the preparation of the pigment dispersion of Example 11.
Next, the water-based ink GJ-8 of the present invention was obtained in the same manner except that the pigment dispersion PD-8 was used instead of the pigment dispersion PD-1 in the preparation of the ink of Example 11.

[Example 19; Preparation of water-based ink GJ-9]
A pigment dispersion PD-9 was obtained in the same manner except that an aqueous solution of the copolymer CP-9 was used instead of the aqueous solution of the copolymer CP-1 in the preparation of the pigment dispersion of Example 11.
Next, the water-based ink GJ-9 of the present invention was obtained in the same manner except that the pigment dispersion PD-9 was used instead of the pigment dispersion PD-1 in the preparation of the ink of Example 11.

[Example 20; Preparation of water-based ink GJ-10]
A pigment dispersion PD-10 was obtained in the same manner except that an aqueous solution of the copolymer CP-10 was used instead of the aqueous solution of the copolymer CP-1 in the preparation of the pigment dispersion of Example 11.
Next, the water-based ink GJ-10 of the present invention was obtained in the same manner except that the pigment dispersion PD-10 was used instead of the pigment dispersion PD-1 in the preparation of the ink of Example 11.

[Example 21; Preparation of water-based ink GJ-11]
In the preparation of the ink of Example 15, instead of 6.0 parts of the urethane resin emulsion UA-368T (manufactured by Sanyo Kasei Co., Ltd.), the acrylic-silicone resin emulsion Polysol ROY6312 (manufactured by Showa High Polymer Co., Ltd., solid content 40.0% by mass) ) 7.5 parts were used, and the water-based ink GJ-11 of the present invention was obtained in the same manner except that 18.0 parts of ion-exchanged water was changed to 16.5 parts.

[Example 22; Preparation of water-based ink GJ-12]
The same applies to the preparation of the ink of Example 15, except that 6.0 parts of urethane resin emulsion UA-368T (manufactured by Sanyo Chemical Industries, Ltd.) is 2.0 parts and 18.0 parts of ion-exchanged water is 22.0 parts. The water-based ink GJ-12 of the present invention was obtained.

[Example 23; Preparation of water-based ink GJ-13]
In the same manner as in the preparation of the ink of Example 15, except that the pigment dispersion PD-1 was changed from 45.0 parts to 56.8 parts and the ion-exchanged water was changed to 6.2 parts. A water-based ink GJ-13 was obtained.

[Example 24; Preparation of water-based ink GJ-14]
In the ink preparation of Example 23, instead of 6.0 parts of urethane resin emulsion UA-368T (manufactured by Sanyo Kasei Co., Ltd.), acrylic-silicone resin emulsion Polysol ROY6312 (manufactured by Showa High Polymer Co., Ltd., solid content 40.0% by mass) ) 7.5 parts and 6.2 parts of ion-exchanged water were set to 4.7 parts, and the water-based ink GJ-14 of the present invention was obtained in the same manner.

[Example 25; Preparation of water-based ink GJ-15]
In the same manner as in the preparation of the ink of Example 15, except that the pigment dispersion PD-1 was changed from 45.0 parts to 37.9 parts and the ion-exchanged water was changed from 18.0 parts to 25.1 parts. Obtained water-based ink GJ-15

[Example 26; Preparation of water-based ink GJ-16]
In the same manner as in the preparation of the ink of Example 15, except that the pigment dispersion PD-1 was changed from 45.0 parts to 33.2 parts and the ion-exchanged water was changed from 18.0 parts to 29.8 parts. Obtained water-based ink GJ-16

[Example 27; Preparation of water-based ink GJ-17]
In the preparation of the ink of Example 26, instead of 6.0 parts of the urethane resin emulsion UA-368T (manufactured by Sanyo Kasei Co., Ltd.), the acrylic-silicone resin emulsion Polysol ROY6312 (manufactured by Showa High Polymer Co., Ltd., solid content 40.0% by mass) ) 7.5 parts and 29.8 parts of ion-exchanged water were set to 28.3 parts, and the water-based ink GJ-17 of the present invention was obtained in the same manner.

[Comparative Example 1; Preparation of Comparative Water-based Ink RGJ-1]
4.82 g of copolymer (weight average molecular weight (Mw): 7500, number) in the same manner except that the monomer M-1 in Example 1 was replaced with a monomer having a structure represented by the following structural formula (7). Average molecular weight (Mn): 2800) was obtained.

Next, using this, an aqueous solution of the comparative copolymer RCP-1 was prepared in the same manner as in Example 11.
That is, the comparative pigment dispersion RPD-1 was obtained in the same manner except that the comparative copolymer RCP-1 was used instead of the copolymer CP-1 in the preparation of the pigment dispersion of Example 11.
Next, a comparative water-based ink RGJ-1 was obtained in the same manner except that the comparative pigment dispersion RPD-1 was used instead of the pigment dispersion 1 in the preparation of the ink of Example 11.

[Comparative Example 2; Preparation of Comparative Water-based Ink RGJ-2]
(Synthesis of Comparative Copolymer RCP-2)
80 g of 2-phenoxyethyl methacrylate as a monomer, 3.7 g of 3-mercapto-1-propanol as a chain transfer agent, and 0.3 g of 2,2-azobis (2,4-dimethylvaleronitrile) as an initiator in 160 mL of THF. It was dissolved, heated to 65 ° C. under a nitrogen atmosphere, and reacted for 7 hours. The obtained solution was allowed to cool, 80 mg of dibutyl tin dilaurate (IV) and a catalytic amount of hydroquinone were added, and 10.0 g of 2-methacryloyloxyethyl isocyanate was added dropwise. After raising the temperature to 50 ° C. and reacting for 2.5 hours, it was purified by reprecipitation with a mixed solvent of methanol and water, and 71 g of macromonomer MM-1 (weight average molecular weight (Mw): 4000, number average). The molecular weight (Mn) was 1900).
Next, 20 g of methyl ethyl ketone was heated to 75 ° C. under a nitrogen atmosphere, followed by 1.16 g of dimethyl 2,2'-azobisisobutyrate, and 1.8 g of the 9 g macromonomer MM-1, obtained above. A solution prepared by dissolving p-styrene sulfonic acid and 49.2 g of methyl methacrylate in 40 g of methyl ethyl ketone was added dropwise over 3 hours. After completion of the dropwise addition, after reacting for another 1 hour, a solution prepared by dissolving 0.2 g of dimethyl 2,2'-azobisisobutyrate in 0.6 g of methyl ethyl ketone was added, the temperature was raised to 80 ° C., and the mixture was heated and stirred for 4 hours. bottom. Further, a solution prepared by dissolving 0.2 g of dimethyl 2,2'-azobisisobutyrate in 0.6 g of methyl ethyl ketone was added, and the mixture was heated and stirred for 6 hours. After cooling, the obtained reaction solution was dropped into hexane, and the precipitated graft polymer was filtered off and dried to obtain a comparative copolymer RCP-2.

(Preparation of Comparative Pigment Dispersion RPD-2, Comparative Aqueous Ink RGJ-2)
Next, a comparative pigment dispersion RPD-2 was obtained in the same manner except that the comparative copolymer RCP-2 was used instead of the copolymer CP-1 in the preparation of the pigment dispersion of Example 11.
Next, a comparative water-based ink RGJ-2 was obtained in the same manner except that the comparative pigment dispersion RPD-2 was used instead of the pigment dispersion PD-1 in the preparation of the ink of Example 11.

[Comparative Example 3; Preparation of Comparative Water-based Ink RGJ-3]
The urethane resin emulsion UA-368T (manufactured by Sanyo Chemical Industries, Ltd., solid content mass 50%) of Comparative Example 1 was changed to 16.0 parts and 18.0 parts of ion-exchanged water to 8.0 parts. A comparative water-based ink RGJ-3 was obtained in the same manner as in Comparative Example 1 except for the above.

[Comparative Example 4; Preparation of Comparative Water-based Ink RGJ-4]
In the preparation of the ink of Comparative Example 1, the pigment dispersion RPD-1 was changed from 45.0 parts to 33.2 parts, and the ion-exchanged water was changed to 29.8 parts in the same manner as in Comparative Example 1. A comparative water-based ink RGJ-4 was obtained.

[Comparative Example 5; Preparation of Comparative Water-based Ink RGJ-5]
In the preparation of the ink of Comparative Example 1, the pigment dispersion RPD-1 was changed from 45.0 parts to 56.8 parts, and the ion-exchanged water was changed to 6.2 parts in the same manner as in Comparative Example 1. A comparative water-based ink RGJ-5 was obtained.

[Comparative Example 6; Preparation of Comparative Water-based Ink RGJ-6]
In the preparation of the ink of Example 15, the same procedure as in Example 15 except that the pigment dispersion PD-5 was changed from 45.0 parts to 59.2 parts and the ion-exchanged water was changed to 3.8 parts. A comparative water-based ink RGJ-6 was obtained.

[Comparative Example 7; Preparation of Comparative Water-based Ink RGJ-7]
In the preparation of the ink of Comparative Example 6, a comparative water-based ink RGJ-7 was obtained in the same manner as in Comparative Example 6 except that the pigment dispersion PD-5 was used as PD-2.

[Comparative Example 8; Preparation of Comparative Water-based Ink RGJ-8]
In the preparation of the ink of Example 15, the comparative water-based ink RGJ- I got 8.

[Comparative Example 9; Preparation of Comparative Water-based Ink RGJ-9]
In the preparation of the ink of Example 15, 6.0 parts of urethane resin emulsion UA-368T (manufactured by Sanyo Chemical Industries, Ltd., solid content mass 50%) was 16.0 parts, and 18.0 parts of ion-exchanged water was 8.0 parts. A comparative water-based ink RGJ-9 was obtained in the same manner as in Example 15 except for the above points.

[Comparative Example 10; Preparation of Comparative Water-based Ink RGJ-10]
In the preparation of the ink of Example 15, 45.0 to 56.8 parts of the pigment dispersion PD-5 and 6.0 parts of the urethane resin emulsion UA-368T (manufactured by Sanyo Kasei Co., Ltd., solid content mass 50%) were 11 parts. A comparative water-based ink RGJ-9 was obtained in the same manner as in Example 15 except that the amount was 0.8 parts and 18.0 parts of ion-exchanged water was 0.4 parts.

The characteristics of each pigment dispersion and ink produced in the above Examples and Comparative Examples were evaluated by the following methods.
Table 2 summarizes the ink formulation contents and results.

<Method for quantifying the amount of resin A>
The amount of resin A in the ink is determined as follows.
1 g of ink is centrifuged at 15,000 rpm for 1 hour using an ultracentrifugation device CP100MX (manufactured by Hitachi, Ltd.) in an environment of 25 ° C. to precipitate the pigment and recover the supernatant. The mass of the supernatant liquid recovered at this time is defined as the amount of the supernatant liquid B (g) in 1 g of the ink. The supernatant is subjected to thermogravimetric analysis using DTG60 (manufactured by Shimadzu Corporation) as follows. 50 mg of the supernatant is placed on a platinum cell, the temperature is raised from 30 ° C. to 120 ° C. at a rate of temperature rise of 10 ° C./min under a nitrogen atmosphere, the temperature is maintained at 120 ° C. for 20 minutes, and the temperature is further raised to 800 ° C. The mass difference between the mass after holding at 120 ° C. and the mass when the temperature is raised at 800 ° C. is the amount of resin contained in 50 mg of the supernatant liquid.
The value of the resin amount A in the ink can be obtained by the following calculation formula.
Amount of resin A (g) = Amount of resin in 1 g of ink A * Ink mass (g) = {{(mass g after holding at 120 ° C.)-(mass g at 800 ° C. temperature rise)} / 0.050 g} * B * Ink mass (g)
B: Amount of supernatant liquid (g) in 1 g of ink
The content of the resin amount A in the ink can be calculated from the resin amount A (g) obtained from the above calculation formula and the mass of the ink.

<Ink storage stability>
Each ink was filled in an ink container and stored at 70 ° C. for one week, and the rate of change in viscosity after storage with respect to the viscosity before storage was calculated from the following formula and evaluated according to the following criteria.
Viscosity change rate (%) = (viscosity of ink after storage / viscosity of ink before storage) x 100
A viscometer (RE80L, manufactured by Toki Sangyo Co., Ltd.) was used to measure the viscosity, and the viscosity at 25 ° C. was measured at 50 rotations.
〔Evaluation criteria〕
A: Viscosity change rate within ± 5% B: Viscosity change rate exceeds ± 5% and within ± 8% C: Viscosity change rate exceeds ± 8% and within ± 10% D: Viscosity change Rate exceeds ± 10% and within ± 30% E: Viscosity change rate exceeds ± 30% (gelled and cannot be evaluated)

<Image density>
64point JIS X 0208 (1997), 2223 general symbols created by Microsoft Word2000 (Microsoft) by filling each ink in an inkjet printer (IPSiO GX5000, manufactured by Ricoh) under a 50% RH environment at 23 ° C. The chart on which is described was printed on MyPaper (manufactured by Ricoh Co., Ltd.), and the symbol portion on the printed surface was color-measured by X-Rite938 (manufactured by X-Rite Co., Ltd.) and evaluated according to the following criteria.
As the print mode, the driver attached to the printer was used to change the "plain paper-standard fast" mode to "no color correction" from the user settings for plain paper.
The above JIS X 0208 (1997), 2223 is a symbol whose outer shape is a regular square and whose entire surface is filled with ink.
〔Evaluation criteria〕
A: 1.25 or more B: 1.20 or more and less than 1.25 C: 1.10 or more and less than 1.20 D: less than 1.10 E: The pigment gels and cannot be dispersed in the ink, so printing is not possible. ..

<Glossy>
Inkjet printer (Ricoh Co., Ltd., IPSIO GX5000) is filled with each ink under a 23 ° C. 50% RH environment, and then gloss recording media (Ricoh Business Coat Gloss 100, background 60 degrees gloss: 21%, A solid image (length 50 mm, width 180 mm) was printed on Ricoh Corporation) under the conditions of an adhesion amount of 9.0 to 10.0 g / m ^{2 and a resolution of 1,200 dpi.} Then, the solid image was dried for 120 seconds in a constant temperature bath set so that the internal temperature was 100 ° C.
Next, the 60-degree glossiness of the solid image was measured using a glossiness meter (Micro-Gloss 60 ° manufactured by Atlas), and based on the following criteria. The glossiness was evaluated.
As for the print mode, the driver attached to the printer used the "glossy paper-clean" mode from the user settings for glossy paper.

<Ink ejection stability>
Regarding the ejection stability, after printing the printed matter, the printer was left in an environment of 50 ° C. for one month with the printer capped on the printer head. Whether or not the ejection state of the printer after being left to stand is restored to the initial ejection state was evaluated according to the following evaluation criteria according to the following number of cleaning operations.
[Evaluation criteria]
A: I was able to print without cleaning.
B: Recovered by 1 to 5 operations.
C: Recovered by 6 to 10 operations.
D: Recovered by 11 to 30 operations.
E: No recovery was observed even after 31 or more movements.

From the results in Table 2, each ink of the example contains a pigment, a copolymer, and resin particles, and the pigment is contained in an amount of 7.0% by mass or more and 12% by mass or less with respect to the ink, and the resin amount A is It is 0.5% by mass or more and 4.0% by mass or less with respect to the total amount of ink, and the 60-degree glossiness of the image formed by using the ink is 25% or more and 51% or less. In comparison, storage stability and ejection stability are good, and high image density can be obtained even with plain paper.

200 Ink container 241 Ink bag 242 Ink inlet 243 Ink outlet 244 Ink container case 400 Image forming device 401 Image forming device exterior 401c Device body cover 404 Cartridge holder 410 Main tank 410k, 410c, 410m, 410y Black (K) ), Cyan (C), Magenta (M), Yellow (Y) Main tank 411 Ink storage 413 Ink outlet 414 Storage container case 420 Mechanical 434 Discharge head 436 Supply tube

Japanese Patent No. 5001291 Japanese Patent No. 49566666 Japanese Patent No. 4722462 Japanese Unexamined Patent Publication No. 2011-105866

Claims (7)

An ink containing pigments, copolymers, and resin particles.
The pigment is contained in an amount of 7.0% by mass or more and 12% by mass or less with respect to the ink.
The content of the resin amount A in the ink is 0.5% by mass or more and 4.0% by mass or less with respect to the ink.
60 degree gloss of the solid image formed by using the ink state, and are 25% or more,
An ink characterized in that the copolymer has structural units represented by the general formula (1) and the general formula (2).

(In the formula, R1 and R2 represent a hydrogen atom or a methyl group, X represents a hydrogen atom or a cation, L represents an alkylene group having 2 to 18 carbon atoms, and * represents a bond site to another structural unit. Represents.
) The ink according to claim 1, wherein the pigment is carbon black. The ink according to claim 1 or 2, wherein the mass ratio of the amount of resin A in the ink to the pigment in the ink is 5% or more and 50% or less. In the copolymer, the molar ratio of the structural units represented by the general formulas (1) and (2) is the general formula (1) :( 2) = 0.5: 1-3: 1. The ink according to any one of claims 1 to 3. The ink according to any one of claims 1 to 4, wherein in the copolymer, L of the structural unit represented by the general formula (2) is an alkylene group having 2 to 12 carbon atoms. An ink container, characterized in that the ink according to any one of claims 1 to 5 is contained in the container. A recording device comprising the means for ejecting ink and the ink according to any one of claims 1 to 5.

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