JP2018065372A - Ink discharge device and ink discharge method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an ink discharge device with low maintenance ink consumption.SOLUTION: An ink flowing out of a flow-out channel flows into a flow-in channel to circulate. The ink comprises water, a colorant, an organic solvent X having an SP value from 8.9 to 12.0 without glycol ether compounds, and a copolymer comprising a structural unit represented by the general formula (1) in the figure. The ink discharge device has negative pressure generation means to generate a negative pressure that lets the ink flow out of the individual liquid chambers.SELECTED DRAWING: None

Description

  The present invention relates to an ink discharge apparatus and an ink discharge method.

As a liquid discharge head (droplet discharge head) for discharging a liquid, a circulation head that circulates liquid in a plurality of individual liquid chambers is known.
For example, a common liquid chamber that supplies a liquid to each individual liquid chamber serving as a pressure generation chamber and a circulation common liquid chamber that communicates with a circulation flow path that communicates with each individual liquid chamber are generated as each individual liquid chamber and circulation flow path. What was formed with the flow-path member comprised with a some plate-shaped member is known (patent document 1).

  Compared to other recording methods, the inkjet recording method is simple because the process is simple, full-colorization is easy, and even a device with a simple configuration has the advantage that high-resolution images can be obtained. It is expanding from personal to office use, commercial printing and industrial printing. In the fields of commercial printing and industrial printing, coated paper such as coated paper and art paper is used as a recording medium in addition to plain paper. The coated paper has a high image density and a high image. Gloss and high fixability are required.

  In the ink jet recording method, dye ink using a water-soluble dye as a coloring material has been mainly used. However, since there is a disadvantage that water resistance and light resistance are inferior, in recent years, instead of the water-soluble dye, Development of pigment inks using insoluble pigments is in progress. When an image is formed on the coated paper using the pigment ink, the organic solvent containing water in the ink is slow to penetrate the coated paper, so that the organic solvent containing water remains on the coated paper surface. In addition, there is a problem in drying and fixing properties such as image loss due to transfer or rubbing.

In order to solve the above problems, for example, in an inkjet ink containing water, a water-soluble organic solvent, a pigment, and a pigment dispersant, and the water content is 10% by mass or more and less than 50% by mass of the total ink mass, Among the water-soluble organic solvents, a water-soluble organic solvent having an SP value of 9 or more and less than 12 is contained by 30% by mass or more based on the total ink, and the acid value of the pigment dispersant is 5 to 160. An ink-jet ink characterized by being a polymer is proposed.
General formula-(A) a- (B) b- (C) c- (D) d- (E) e-
(In the formula, A, B, C, D and E represent monomers constituting the pigment dispersant, and a, b, c, d and e are constituent molar ratios of the respective monomers in the pigment dispersant. A is a monomer containing an acidic group of a carboxylic acid or sulfonic acid and a salt derivative thereof, B is a monomer containing a hydroxy group, and C is a straight chain or branched chain having 8 or more carbon atoms. D represents styrene and derivatives thereof, E represents other polymerizable monomers, a represents 1 to 24%, b represents 1 to 60%, c And d is 1 to 50%, and c + d is 5 to 50%. E is 0 to 40%.) (For example, see Patent Document 2)

However, the conventional ink-jet ink has a problem that when the ink is continuously ejected for a long period of time, the ejection of the ink is disturbed and an image is defective.
The present invention is not only plain paper, but also commercial printing paper, which is highly dry and excellent in productivity, can be recorded with good quality with suppressed beading, and has less image disturbance. An object of the present invention is to provide an ink ejection apparatus that consumes less maintenance ink.

The above-described problem is solved by the following <1> invention.
<1> Ink, nozzle for ejecting the ink, a plurality of individual liquid chambers communicating with the nozzle, an inflow channel for allowing the ink to flow into the individual liquid chamber, and an outflow for allowing the ink to flow out from the individual liquid chamber An ink discharge device comprising: an ink discharge head having a path, wherein the ink flowing out from the outflow channel flows into the inflow channel and circulates;
The ink contains an organic solvent X having a solubility parameter (SP value) of 8.9 or more and 12.0 or less excluding water, a coloring material, and a glycol ether compound, and a copolymer.
The copolymer has a structural unit represented by the following general formula (1),
The ink discharge apparatus includes a negative pressure generating unit that generates a negative pressure that causes the ink to flow out of the individual liquid chamber.
(In the above formula, R1 represents a hydrogen atom or a methyl group. Y represents an alkylene group having 2 to 18 carbon atoms.)

  According to the present invention, not only plain paper but also commercial printing paper can be recorded with good quality with excellent dryness and excellent productivity, with reduced beading, and image distortion. It is possible to provide an ink ejection device that consumes less maintenance ink.

1 is a perspective view schematically illustrating an example of an ink ejection device according to the present invention. It is a perspective view which shows typically an example of the ink storage container which concerns on this invention. FIG. 2 is an explanatory perspective view of the appearance of an ink discharge head according to an embodiment of the present invention. It is sectional explanatory drawing of the direction orthogonal to the nozzle arrangement direction of the head. It is a partial cross section explanatory view of a direction parallel to the nozzle arrangement direction of the head. It is a plane explanatory view of the nozzle plate of the head. It is a plane explanatory view of each member which constitutes a channel member of the head. It is a plane explanatory view of each member which constitutes a common liquid chamber member of the head. It is a block diagram which shows an example of the ink circulation system which concerns on this invention. It is principal part plane explanatory drawing of an example of the ink discharge apparatus which concerns on this invention. It is principal part side explanatory drawing of the apparatus. It is principal part plane explanatory drawing of the other example of the ink discharge unit which concerns on this invention. It is explanatory drawing which shows typically an example of the ink discharge apparatus which concerns on this invention.

Hereinafter, although the present invention <1> will be described in detail, the following <2> to <12> are also included in the embodiment, and these will also be described together.
<2> The ink ejection device according to <1>, wherein the copolymer further includes a structural unit represented by the following general formula (2).
(In the above formula, R2 represents a hydrogen atom or a methyl group. M represents a hydrogen atom, an alkali metal or organic ammonium.)
<3> The ratio of the content of the organic solvent X contained in the ink to the total content of water and the organic solvent X contained in the ink {organic solvent X / (organic solvent X + water)} is 20% by mass or more. The ink ejection device according to <1> or <2>.
<4> The ink ejection device according to any one of <1> to <3>, wherein the ink includes a glycol ether compound (compound Z) having a vapor pressure of 50 mmHg or more in an environment of 100 ° C.
<5> The ink ejection device according to <4>, wherein the compound Z is at least one selected from propylene glycol monopropyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and propylene glycol monobutyl ether.
<6> The ink ejection device according to <4> or <5>, wherein a ratio (mass ratio) of the content of the organic solvent X and the compound Z is 1: 1 to 8: 1.
<7> The organic solvent X is at least one selected from compounds represented by the following general formula (3), general formula (4), and formula (5), and any one of <1> to <6> The ink ejection apparatus according to claim.
(In the above formula, R3 represents an alkyl group having 4 to 6 carbon atoms.)
(In the above formula, R4 represents an alkyl group having 1 to 2 carbon atoms.)
<8> The ink contains a wax, and the mass ratio (x / w) of the content x of the organic solvent X to the content w of the wax in the ink satisfies 30 ≦ x / w ≦ 500 <1 > The ink ejection device according to any one of <7>.
<9> The ink ejection device according to <8>, wherein the wax has a melting point of 100 ° C to 140 ° C.
<10> The ink ejection apparatus according to any one of <1> to <9>, wherein the ink contains a polyether-modified siloxane compound.
<11> The <1> to <10>, wherein the ink has a static surface tension of 20 mN / m or more and a dynamic surface tension of 34 mN / m or less at a bubble lifetime of 15 msec by a maximum bubble pressure method. Any one of the ink discharge apparatuses.
<12> Ink, nozzle for ejecting the ink, a plurality of individual liquid chambers communicating with the nozzle, an inflow channel for allowing the ink to flow into the individual liquid chamber, and an outflow for allowing the ink to flow out from the individual liquid chamber An ink ejection head having a path, and an ink ejection device that circulates the ink flowing out from the outflow channel by flowing into the inflow channel,
The ink contains an organic solvent X having a solubility parameter (SP value) of 8.9 or more and 12.0 or less excluding water, a coloring material, and a glycol ether compound, and a copolymer.
The copolymer has a structural unit represented by the following general formula (1),
An ink discharge method comprising a negative pressure generating step of generating a negative pressure for causing the ink to flow out of the individual liquid chamber.
(In the above formula, R1 represents a hydrogen atom or a methyl group. Y represents an alkylene group having 2 to 18 carbon atoms.)

<Ink>
The ink used in the present invention contains an organic solvent X having a solubility parameter (SP value) of 8.9 or more and 12.0 or less excluding water, a coloring material, and a glycol ether compound, and a copolymer having a specific structure.

-Copolymer having a specific structure-
The copolymer having a specific structure used in the present invention will be described.
In the ink ejection apparatus of the present invention, the circulation type ejection head is combined with an ink containing a solvent having a low solubility parameter (SP value). In such a circulation type discharge head, since the ink does not flow out from the nozzle, a negative pressure tank is required in the circulation path, and the pressure is always reduced by a vacuum pump to maintain the negative pressure. Under such negative pressure, the water in the ink tends to volatilize, so the ink changes to a hydrophobic composition, and the balance between hydrophilicity and hydrophobicity changes, so that the dispersion stability of the pigment contained in the ink is stable. There is a problem that the property is impaired. If it is a normal polymer dispersant, it becomes unstable in such a hydrophobic ink solvent, the dispersion stability of the pigment is impaired, and problems such as nozzle omission and ejection bending occur. The copolymer having the structure represented by the general formula (1) in the present invention is very excellent in solvent resistance as compared with a general copolymer. Even in such a hydrophobic ink solvent, the pigment in the ink is used. Can be dispersed stably. Therefore, even after the ink is circulated under a negative pressure in the circulation tank, a good discharge property and a high-quality image can be obtained.
The reason why such excellent solvent resistance is manifested is that the naphthyl group of the side chain of the general formula (1) in the copolymer in this case is strongly adsorbed by the hydrophobic interaction with the pigment. .

The copolymer has a structural unit represented by the following general formula (1).
In the above formula, R1 represents a hydrogen atom or a methyl group. Y represents an alkylene group having 2 to 18 carbon atoms.
The content of the structural unit represented by the general formula (1) in the copolymer is usually 10 mol% or more and 90 mol% or less, and preferably 30 mol% or more and 70 mol% or less. When the content of the structural unit represented by the general formula (1) is 30 mol% or more, the solvent resistance of the ink can be improved, and when it is 70 mol% or less, the dispersion stability of the pigment in the ink Can be improved.
In addition, the content of the copolymer having the structural unit represented by the general formula (1) in the ink of the present invention is usually 0.1% by mass or more and 10.0% by mass or less, and 0.5% by mass. % Or more and 5.0% by mass or less is preferable. When the copolymer content is 0.5% by mass or more, the maintenance consumption of the ink can be further reduced, and when it is 10.0% by mass or less, the ejection reliability is further improved. Can do.

The copolymer polymerizes a monomer represented by the following general formula (I) with, for example, a polymerizable monomer having an anionic hydrophilic functional group, a polymerizable hydrophobic monomer, a polymerizable surfactant, and the like. It is obtained by doing. If necessary, a polymerizable monomer having a hydrophilic functional group other than anionic, for example, a polymerizable monomer having a cationic hydrophilic functional group or a polymerizable monomer having a nonionic hydrophilic functional group is added. You may do it.
In the above formula, R1 represents a hydrogen atom or a methyl group. Y represents an alkylene group having 2 to 18 carbon atoms.

The monomer represented by the general formula (I) can be synthesized using conventionally known monomers such as 1-vinylnaphthalene and 2-vinylnaphthalene.
Moreover, the monomer represented with general formula (I) can be obtained by making the reactive compound which has a naphthyl group in a molecule | numerator, and a polymerizable monomer react.

  Examples of the reactive compound having a naphthyl group in the molecule include naphthalenecarboxylic acid hydroxyethyl ester, naphthalenecarboxylic acid hydroxypropyl ester, naphthalenecarboxylic acid hydroxybutyl ester, and the like. Examples of the monomer to be reacted with these reactive compounds include 2-acryloyloxyethyl isocyanate and 2-methacryloyloxyethyl isocyanate.

  Examples of polymerizable monomers having an anionic hydrophilic functional group include unsaturated carboxylic acids such as acrylic acid, methacrylic acid, maleic acid, and itaconic acid, 2-methacryloyloxyethyl acid phosphoate, and 2-acryloyl. Unsaturated phosphoric acid such as oxyethyl acid phosphoate, acid phosphooxy polyoxyethylene glycol methacrylate, acid phosphooxy polyoxyethylene glycol methacrylate, acid phosphooxy poly (oxyethyleneoxypropylene) glycol methacrylate, vinyl sulfonic acid, styrene sulfonic acid , Unsaturated sulfonic acids such as 4-styrenesulfonic acid, 2-acrylamido-2-methylpropanesulfonic acid, 2-hydroxy-3-allyloxy-1-propanesulfonic acid, or phosphorus , Phosphonic acid, such as anionic ethylenically unsaturated monomers such as ethylenically unsaturated monomers containing alendronate or etidronate and the like.

Examples of the anionic hydrophilic functional group possessed by the copolymer in the present invention include the following, but are not limited thereto. Among these anionic hydrophilic functional groups, a carboxyl group is particularly preferable. When the anionic hydrophilic functional group is a carboxyl group, beading on the coated paper is good.
_{^{-COO -, -SO 3 -, -PO}} 3 H -, -PO 3 2-, -CON 2-, -SO 3 N 2-, -NH-C 6 H 4 -COO -, -NH-C 6 H ^{_{4 -SO 3 -, -NH-C}} 6 H 4 -PO 3 H -, -NH-C 6 H 4 -PO 3 2-, -NH-C 6 H 4 -CON 2-, -NH-C 6 H _4- SO ₃ N ^2-

The copolymer in the present invention preferably has a structural unit represented by the general formula (1), and further has a structural unit represented by the following general formula (2).
In the above formula, R2 represents a hydrogen atom or a methyl group. M represents a hydrogen atom, an alkali metal, or organic ammonium.
As will be described later, the copolymer is preferably a salt, and when a base is added to neutralize the copolymer, the added base exists as a cation.

  Examples of the polymerizable hydrophobic monomer include unsaturated ethylene monomers having an aromatic ring such as α-methylstyrene, 4-t-butylstyrene, 4-chloromethylstyrene; methyl (meth) acrylate, (meta ) Ethyl acrylate, (n-butyl) (meth) acrylate, dimethyl maleate, dimethyl itaconate, 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), nonadecyl (meth) acrylate (C19), (meth) Eicosyl acrylate (C20), helicosyl (meth) acrylate (C21), Alkyl (meth) acrylates such as docosyl methacrylate (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, -Nonene, 3,5,5-trimethyl-1-hexene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, 1-pentadecene, 1-hexadecene, 1-heptadecene, 1-octadecene , Unsaturated ethylene monomers having an alkyl group such as 1-nonadecene, 1-eicosene and 1-docosene. These may be used individually by 1 type and may use 2 or more types together.

The polymerizable surfactant is an anionic or nonionic surfactant having at least one unsaturated double bond group capable of radical polymerization in the molecule.
Examples of the anionic surfactant, ammonium sulfate base (-SO ₃ ^- NH ₄ ⁺⁾ hydrocarbon compound having a sulfate group and an allyl group (-CH ₂ -CH = CH _2), such as, ammonium sulfate base (-SO ₃ ^- NH ₄ ⁺⁾ sulfate group and methacrylic group, such as _{[-CO-C (CH 3) =} CH 2 ] a hydrocarbon compound having, or ammonium sulfate base (-SO ₃ ^- NH ₄ ⁺⁾ sulfate, such as base and 1 An aromatic hydrocarbon compound having a —propenyl group (—CH═CH ₂ CH ₃ ) is exemplified. Specific examples include Eleminol JS-20 and RS-300 manufactured by Sanyo Kasei Co., Ltd., Aqualon KH-10, Aqualon KH-1025, Aqualon KH-05, Aqualon HS-10, Aqualon HS, manufactured by Daiichi Kogyo Seiyaku Co., Ltd. -1025, Aqualon BC-0515, Aqualon BC-10, Aqualon BC-1025, Aqualon BC-20, and Aqualon BC-2020.

Examples of the nonionic surfactant include hydrocarbon compounds or aromatics having a 1-propenyl group (—CH═CH ₂ CH ₃ ) and a polyoxyethylene group [— (C ₂ H ₄ O) n—H]. A hydrocarbon compound is mentioned. Specific examples thereof include Aqualon RN-20, Aqualon RN-2025, Aqualon RN-30, and Aqualon RN-50 manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Latemu PD-104, Latemu PD-420, Latemu PD manufactured by Kao Corporation -430, Latem PD-450, and the like.
The polymerizable surfactants may be used alone or in combination of two or more.

Examples of the polymerizable monomer having a nonionic hydrophilic functional group include (meth) acrylic acid-2-hydroxyethyl, diethylene glycol mono (meth) acrylate, triethylene glycol mono (meth) acrylate, and tetraethylene glycol mono. (Meth) acrylate and polyethylene glycol mono (meth) acrylate.
Examples of the polymerizable monomer having a cationic hydrophilic functional group include (meth) acrylamide, N-methylol (meth) acrylamide, N-vinylformamide, N-vinylacetamide, N-vinylpyrrolidone, and acrylamide. N, N-dimethylacrylamide, Nt-butylacrylamide, N-octylacrylamide, Nt-octylacrylamide and the like.

  As a method for synthesizing the copolymer, various known synthesis methods such as solution polymerization, suspension polymerization, bulk polymerization, emulsion polymerization and the like can be used, but since the polymerization operation and the adjustment of the molecular weight are easy, A method using a radical polymerization initiator is preferred.

  As the radical polymerization initiator, those generally used can be used, and specifically, peroxyketals, hydroperoxides, dialkyl peroxides, diacyl peroxides, peroxydicarbonates, peroxyesters, cyano series Azobisisobutyronitrile, azobis (2-methylbutyronitrile), azobis (2,2′-isovaleronitrile), non-cyano dimethyl-2,2′-azobisisobutyrate, and the like. . Organic peroxides and azo compounds that can easily control the molecular weight and have a low decomposition temperature are preferable, and azo compounds are more preferable. As for the usage-amount of a polymerization initiator, 1-10 mass% is preferable with respect to the total mass of a polymerizable monomer.

  The weight average molecular weight of the copolymer is preferably 5,000 or more and 40,000 or less because the storage stability, image density, glossiness, and ejection reliability of the pigment dispersion / ink are further improved.

The copolymer of the present invention is preferably a salt. In the ink, the base added to neutralize the copolymer is present as a cation.
The amount of cation added is from 1 to 2 times the number of moles of anionic hydrophilic functional group contained in the copolymer, since the storage stability of the pigment dispersion and the storage stability of the ink are further improved. Is preferred.
As the cation, an organic ammonium ion is preferable because the ink storage stability is further improved.
The amount of cation contained in the ink can be calculated from the prescribed amount, but can also be determined by analyzing the ink itself.
If the cation is a metal ion, the cation contained in the ink can be determined by an ICP emission spectroscopic analyzer. Examples of the ICP emission spectroscopic analyzer include ICPE-9000 (manufactured by Shimadzu Corporation), Optima 8000 (manufactured by PerkinElmer) and the like.
If the cation is organic ammonium, the amount of cation in the ink can be determined by GC / MS analysis. Examples of the GC / MS analyzer include GCMS-QP2010 Ultra (manufactured by Shimadzu Corporation), Agilent 7000C (manufactured by Agilent Technologies), and the like.

Although it does not specifically limit as a cation, A sodium ion, potassium ion, lithium ion, organic ammonium ion, etc. are mentioned.
As organic ammonium ions, tetramethylammonium ion, tetraethylammonium ion, tetrapropylammonium ion, tetrabutylammonium ion, tetrapentylammonium ion, tetrahexylammonium ion, triethylmethylammonium ion, tributylmethylammonium ion, trioctylmethylammonium ion 2-hydroxyethyltrimethylammonium ion, tris (2-hydroxyethyl) methylammonium ion, propyltrimethylammonium ion, hexyltrimethylammonium ion, octyltrimethylammonium ion, nonyltrimethylammonium ion, decyltrimethylammonium ion, dodecyltrimethylammonium ion , Tetradecyltrimethylammonium ion, hexadecyltrimethylammonium ion, octadecyltrimethylammonium ion didodecyldimethylammonium ion, ditetradecyldimethylammonium ion, dihexadecyldimethylammonium ion, dioctadecyldimethylammonium ion, ethylhexadecyldimethylammonium ion, Ammonium ion, dimethyl ammonium ion, trimethyl ammonium ion, monoethyl ammonium ion, diethyl ammonium ion, triethyl ammonium ion, monoethanol ammonium ion, diethanol ammonium ion, triethanol ammonium ion, methyl ethanol ammonium ion, methyl diethanol ammonium ion Ion, dimethyl ethanol ammonium ion, mono-propanol ammonium ion, dipropanol ammonium ion, tri-propanol ammonium ion, isopropanol ammonium ion, and the like. As the cation, an organic ammonium ion is preferable because ink storage stability and ejection reliability are improved.

-Organic solvent-
The ink of the present invention contains at least one organic solvent (organic solvent X) having an SP value of 8.9 to 12.0 excluding the glycol ether compound. Thereby, the wettability with respect to the recording medium is improved, and the ink component penetrates into commercial printing paper such as coated paper having a coating layer and poor ink-absorbing property, and beading can be suppressed.

The organic solvent (organic solvent X) having an SP value of 8.9 or more and 12.0 or less excluding the glycol ether compound is more permeable to the coated paper than the ordinary organic solvent, and ejects ink onto the coated paper. When an image is formed, beading hardly occurs and the amount of ink remaining on the coated paper is reduced, so that blocking is unlikely to occur and the productivity is excellent. However, when an ink using such a solvent is used in combination with a circulation discharge type head, the ink is placed in a long-term negative pressure environment, water in the ink volatilizes, and the composition of the ink has a very low SP value. , The state becomes very hydrophobic. In such a state, the ordinary dispersant has a weak function as a dispersant and the dispersion of the pigment becomes unstable, but the copolymer having the structural unit represented by the general formula (1) of the present invention is used. If so, the pigment can be stably dispersed even in the above highly hydrophobic state, and image defects such as nozzle omission and ejection disturbance are unlikely to occur.
The organic solvent X is preferably water-soluble, and particularly preferably the amide compound of the general formula (3) or the formula (5) or the oxetane compound of the general formula (4).
An organic solvent having an SP value of less than 8.9 generally has very low solubility in water and is likely to be separated, so that it cannot be used in a water-based ink as in the present invention. Moreover, an organic solvent having an SP value exceeding 12.0 cannot be used because drying properties and beading deteriorate.
The SP value is a value defined by the regular solution theory introduced by Hildebrand and is a measure of the solubility of the binary solution. The SP value in the present invention is a value calculated by the Fedors method. It is indicated by the square root of the cohesive energy density in regular solution theory, and the unit is (cal / cm ³ ) ^0.5 . It can be calculated with simple software that is widely used.

Examples of the amide compound represented by the general formula (3) include compounds of the following formulas (3-1) to (3-3).

Examples of the oxetane compound represented by the general formula (4) include compounds represented by the following formulas (4-1) to (4-2).
The SP value of the amide compound of the formula (5) is 10.3.
Examples of other organic solvents X include “2-ethyl-1,3-hexanediol” (SP value: 10.6), “2,2,4-trimethyl-1,3-pentanediol” ( SP value: 10.8).

  The content of the organic solvent X is preferably 10% by mass or more, more preferably 20 to 60% by mass, based on the entire ink. If the content is 20% by mass or more, beading on commercial printing paper and color bleeding between colors can be sufficiently obtained. Further, when the content is 60% by mass or less, the ejection stability is not deteriorated due to an increase in the viscosity of the ink.

  The ratio of the content of the organic solvent X contained in the ink to the total content of water and the organic solvent X contained in the ink {organic solvent X / (organic solvent X + water)} is 20% by mass or more. Preferably, it is 20 mass% or more and 60 mass% or less. Since the organic solvent X / (organic solvent X + water) is 20% by mass or more, a sufficient amount of the organic solvent X remains in the ink even after the ink is circulated for a long time under a negative pressure in the circulation discharge type head. As a result, the fluidity of the ink is ensured and the ejection reliability is improved. Further, when the organic solvent X / (organic solvent X + water) is 60% by mass or less, the drying property of the ink is further improved.

  Furthermore, in the present invention, by including a glycol ether compound (hereinafter referred to as “Compound Z”) having a vapor pressure of 50 mmHg or more in an environment of 100 ° C. as an organic solvent, the drying property is improved, and even on commercial printing paper. In addition to improving the drying property, the image is not transferred even if the image portion comes into contact with the conveying roller immediately after drying with hot air at 100 ° C., and high-speed productivity is ensured. The compound Z is more volatile than an organic solvent having an SP value of 8.9 to 12.0, and an ink containing the organic solvent having an SP value of 8.9 to 12.0 and the compound Z is used for the circulation discharge type head. Then, the compound Z volatilizes first, and the ink solvent becomes more hydrophobic.

  The compound Z is preferably one that dissolves in high purity water. Examples thereof include propylene glycol monopropyl ether (bp 150 ° C., vapor pressure 107 mmHg), propylene glycol monoethyl ether (bp 133 ° C., vapor pressure 252 mm Hg), propylene glycol monomethyl ether (bp 120 ° C., vapor pressure 360 mm Hg), propylene glycol monobutyl ether (Bp 170 ° C., vapor pressure 59 mmHg).

The content ratio (mass ratio) of the organic solvent X and the compound Z in the ink is preferably 1: 1 to 8: 1. Furthermore, it is preferable to set it as 3: 1-5: 1. When this ratio is 1: 1 or more, that is, when the content of the organic solvent X is more than the content of the compound Z, the ink jet head is not dried too much and the inside of the ink jet head is dried, which causes a problem in ejection stability. Will not occur. Further, when the ratio is 8: 1 or less, the organic solvent X is not too much, so that the drying property on the commercial printing paper is lowered and the productivity is not lowered.
In the present invention, the organic solvent is an organic solvent X (an organic solvent having an SP value of 8.9 to 12.0 excluding a glycol ether compound), a compound Z (a glycol ether having a vapor pressure of 50 mmHg or more in an environment of 100 ° C. Compound), and other organic solvents that do not belong to any of organic solvent X and compound Z.

  The total content of the organic solvent in the ink containing the organic solvent X and the compound Z is preferably 20 to 60% by mass of the whole ink. If it is 20 mass% or more, the beading suppression effect on commercial printing paper will not decrease. On the other hand, when the amount is 60% by mass or less, the ink viscosity is remarkably increased, and there is no problem in ejection stability.

-Other solvents (humectants)-
The other solvent (humectant) is not particularly limited as long as it is not the organic solvent X or glycol tetral compound, but a polyhydric alcohol is preferred. For example, glycerin, triethylene glycol, 1,2,6-hexanetriol, 2-ethyl-1,3-hexanediol, ethyl-1,2,4-butanetriol, 1,2,3-butanetriol, 2, 2,4-trimethyl-1,3-pentanediol, petriol and the like are listed.

-Water-
Examples of water include pure water such as ion exchange water, ultrafiltration water, reverse osmosis water, and distilled water, high pure water, and ultrapure water. The water content in the ink is preferably 20 to 60% by mass.

-Color material-
Surfactant dispersion in which pigment is dispersed with surfactant, resin dispersion in which pigment is dispersed in resin, resin coating dispersion in which pigment surface is coated with resin, and self-dispersed pigment with hydrophilic group on pigment surface However, water dispersible ones are preferred. Among them, the resin-coated pigment or the self-dispersing pigment that has at least one hydrophilic group on the pigment surface is preferable.
Such hydrophilic _{groups, -COOM, -SO 3 M, -PO} 3 HM, -PO 3 M 2, -CONM 2, -SO 3 NM 2, -NH-C 6 H 4 -COOM, -NH- _{C 6 H 4 -SO 3 M,} -NH-C 6 H 4 -PO 3 HM, -NH-C 6 H 4 -PO 3 M 2, -NH-C 6 H 4 -CONM 2, -NH-C 6 H ₄ —SO ₃ NM ₂ (M represents a counter ion). These hydrophilic groups can be introduced by a known method.

  The counter ion M is preferably a quaternary ammonium ion. Specific examples thereof include tetramethylammonium ion, tetraethylammonium ion, tetrapropylammonium ion, tetrabutylammonium ion, tetrapentylammonium ion, benzyltrimethylammonium ion, benzyltriethylammonium ion and tetrahexylammonium ion, and tetraethylammonium ion. Ions, tetrabutylammonium ions and benzyltrimethylammonium ions are preferred, and tetrabutylammonium ions are particularly preferred.

  The ink using the above pigment has particularly high storage stability with time and suppresses an increase in viscosity when moisture evaporates. This is presumably because the dispersion of the pigment can be kept stable by the hydrophilic group having a quaternary ammonium ion even when water is evaporated from the water-rich ink and becomes rich in the organic solvent.

  As the coloring material other than the pigment having a hydrophilic group, a polymer emulsion in which a pigment is contained in polymer fine particles is preferable. The pigment may be encapsulated in the polymer fine particles or may be adsorbed on the surface of the polymer fine particles. In this case, it is not necessary for all the pigments to be encapsulated or adsorbed, and a part of them may be dispersed in the emulsion. Examples of the polymer for polymer fine particles include vinyl polymers, polyester polymers, polyurethane polymers, and the like, and vinyl polymers and polyester polymers are particularly preferable. Specific examples thereof include those disclosed in JP-A Nos. 2000-53897 and 2001-139849.

  Further, a general organic pigment or a composite pigment obtained by coating inorganic pigment particles with an organic pigment or carbon black can also be used. The composite pigment can be produced by a method of depositing an organic pigment in the presence of inorganic pigment particles, a mechanochemical method of mechanically mixing and grinding an inorganic pigment and an organic pigment, or the like. Furthermore, the adhesiveness of both can also be improved by providing the layer of the organosilane compound produced | generated from polysiloxane and alkylsilane as needed between the inorganic pigment and the organic pigment.

  The mass ratio between the inorganic pigment particles and the organic pigment or carbon black of the coloring material is preferably 3: 1 to 1: 3, and more preferably 3: 2 to 1: 2. If there are few color materials, color developability and coloring power may fall, and if there are many color materials, transparency and a color tone may worsen.

  As the composite pigment, silica / carbon black composite material manufactured by Toda Kogyo Co., Ltd., silica / phthalocyanine PB15: 3 composite material, silica / disazo yellow composite material, silica / quinacridone PR122 composite material, etc. have a small primary average particle size. Is preferred.

  Here, when inorganic pigment particles having a primary particle size of 20 nm are coated with an equal amount of organic pigment, the primary particle size of the pigment is about 25 nm. If a primary dispersant can be dispersed using a suitable dispersant for this, a very fine pigment-dispersed ink having a dispersed particle diameter of 25 nm can be produced. The composite pigment not only contributes to the dispersion of the organic pigment on the surface, but also exhibits the properties of an inorganic pigment at the center through a thin layer of an organic pigment having a thickness of about 2.5 nm. The selection of the pigment dispersant is also important.

  Examples of the inorganic pigment include titanium oxide, iron oxide, calcium carbonate, barium sulfate, aluminum hydroxide, barium yellow, cadmium red, chrome yellow, and carbon black. Among these, carbon black is particularly preferable, and examples thereof include channel black, furnace black, gas black, and lamp black produced by known methods such as a contact method, a furnace method, and a thermal method.

  Examples of the organic pigment include azo pigments, polycyclic pigments, dye chelates, nitro pigments, nitroso pigments, and aniline black. Among these, azo pigments and polycyclic pigments are preferable. Examples of the azo pigment include azo lakes, insoluble azo pigments, condensed azo pigments, and chelate azo pigments. Examples of the polycyclic pigment include phthalocyanine pigments, perylene pigments, perinone pigments, anthraquinone pigments, quinacridone pigments, dioxazine pigments, indigo pigments, thioindigo pigments, isoindolinone pigments, and quinofullerone pigments. Examples of the dye chelates include basic dye chelates and acidic dye chelates.

Examples of the organic pigment include C.I. I. Pigment Yellow 1, 3, 12, 13, 14, 17, 24, 34, 35, 37, 42 (yellow iron oxide), 53, 55, 74, 81, 83, 95, 97, 98, 100, 101, 104 , 408, 109, 110, 117, 120, 128, 139, 150, 151, 155, 153, 180, 183, 185, 213, C.I. I. Pigment orange 5, 13, 16, 17, 36, 43, 51, C.I. I. Pigment Red 1, 2, 3, 5, 17, 22, 23, 31, 38, 48: 2, 48: 2 (Permanent Red 2B (Ca)), 48: 3, 48: 4, 49: 1, 52: 2, 53: 1
57: 1 (Brilliant Carmine 6B), 60: 1, 63: 1, 63: 2, 64: 1, 81, 83, 88, 101 (Bengara), 104, 105, 106, 108 (Cadmium Red), 112 114, 122 (quinacridone magenta), 123, 146, 149, 166, 168, 170, 172, 177, 178, 179, 185, 190, 193, 209, 219, C.I. I. Pigment violet 1 (rhodamine lake), 3, 5: 1, 16, 19, 23, 38, C.I. I. Pigment Blue 1, 2, 15 (phthalocyanine blue), 15: 1, 15: 2, 15: 3 (phthalocyanine blue), 16, 17: 1, 56, 60, 63; I. Pigment green 1, 4, 7, 8, 10, 17, 18, 36, and the like.

The BET specific surface area of the pigment used is preferably about 10 to about 1500 m ² / g, more preferably about 20 to about 600 m ² / g, and still more preferably about 50 to about 300 m ² / g.
If it is not easy to use a material having a desired specific surface area, a general size reduction or grinding process (for example, ball milling, jet milling, sonication) is performed to make the pigment relatively small in particle size. Just do it.

The volume average particle diameter (D ₅₀ ) of the water dispersible colorant is preferably 10 to 200 nm in the ink.
The content of the water-dispersible color material in the ink is preferably 1 to 15% by mass and more preferably 2 to 10% by mass in terms of solid content. When the content is 1% by mass or more, the color developability and image density of the ink are improved. preferable.
In the present invention, a dye may be used in combination for the purpose of adjusting the color tone, but it is necessary to use it within a range that does not deteriorate the weather resistance.

-Wax-
The ink contains a wax, and the mass ratio (x / w) of the content x of the organic solvent X to the content w of the wax in the ink is preferably 30 ≦ x / w ≦ 500.
When using the above-mentioned pigment ink, there is a problem in drying and fixing properties such as image loss due to transfer or rubbing. Abrasion can be improved. However, wax has a strong hydrophobic property, and when it is added to an ink having a strong hydrophilic property, the storage property and the discharge property are lowered. For this reason, a solvent having an SP value of 9.0 or more and 11.0 or less is included, and the ratio (mass basis) of the wax content in the ink and the solvent having an SP value of 9.0 or more and 11.0 or less. However, an ink in the range of 1: 2.5 to 1: 25.0 is proposed in Japanese Patent Application Laid-Open No. 2006-145313. However, when this ink is used in the circulation head of the present invention, there arises a problem that the dispersion of the pigment is broken in the negative pressure tank due to the hydrophobic effect of the solvent and the wax. Therefore, in the present invention, the amount of wax is reduced within a range that does not cause a problem in image fixability, and the solubility parameter (SP value) with respect to the wax content w in the ink is 8.9 or more and 12.0 or less. The ratio (x / w) of the X content x is preferably 30 ≦ x / w ≦ 500.

  The wax contained in the ink according to the present invention may be either water-soluble or water-dispersible. The water-soluble wax can be used mainly as a wax emulsion as a wax having a hydrophilic group such as a hydroxyl group, a carboxyl group, an ethylene oxide group or an amine group, and as a water-dispersible wax.

  More specifically, plants such as carnauba wax, candelilla wax, beeswax, rice wax, lanolin, and other petroleum waxes such as animal wax, paraffin wax, microcrystalline wax, polyethylene wax, polypropylene wax, oxidized polyethylene wax, petrolatum, etc. , Mineral waxes such as montan wax, ozokerite, synthetic waxes such as carbon wax, Hoechst wax, polyethylene wax, stearamide, natural / synthetic wax emulsions such as α-olefin / maleic anhydride copolymer and blended wax, etc. Can be used alone or in admixture of two or more. Other latexes, colloidal solutions, suspensions, and the like can also be used. In the present invention, a polyethylene wax having good solubility and dispersibility with a water-soluble solvent is desirable.

  A commercially available wax may be used. Specific examples thereof include cellosol 524 (carnauba wax, melting point 83 ° C., particle size 200 nm, manufactured by Chukyo Yushi), HYTEC E-6500 (polyethylene wax, melting point 140 HYTEC E-8237 (polyethylene wax, melting point 106 ° C., particle size 80 nm, manufactured by Toho Chemical), HYTEC P-9018 (polypropylene wax, melting point 156 ° C., particle size 60 nm, Toho Chemical) Nopcoat PEM-177 (polyolefin wax, melting point 105 ° C., particle size 10 nm, manufactured by San Nopco), AQUACER 498 (paraffin wax, melting point 58 ° C., manufactured by Big Chemie Japan), AQUACER 535 (mixed wax, melting point 95 ° C., Bic Chemie Japan AQUACER 531 (polyethylene wax, melting point 130 ° C., particle size 123 nm, manufactured by Big Chemie Japan), AQUACER 515 (polyethylene wax, melting point 135 ° C., particle size 33 nm, manufactured by Big Chemie Japan) and the like.

  The melting point of the wax is preferably in the range of 70 ° C to 170 ° C, more preferably 100 ° C to 140 ° C. If the melting point is 70 ° C. or higher, the image will not be sticky, and image transfer will not occur even if the images are superimposed. When the melting point is 170 ° C. or lower, the image is melted by frictional heat when the image is rubbed and slipperiness is obtained, so that the image has good scratch resistance.

  The volume average particle diameter of the wax is preferably 200 nm or less, more preferably 20 nm to 150 nm. If it is 200 nm or less, it will not be caught by the filter in a nozzle or a head, and favorable discharge will be obtained.

  The amount of the wax solid content added to the ink is preferably in the range of 0.05 to 2% by mass, more preferably 0.1 to 0.5% by mass. When the addition amount is 0.1% by mass or more, slipperiness can be imparted to the image surface after printing, and the scratch resistance of the image can be maintained high. Further, when the addition amount is 0.5% by mass or less, the wax can be dissolved or dispersed in the solvent in the ink, so that it does not deposit and adhere to the head. It becomes possible.

The ratio (x / w) of the content x of the organic solvent X to the content w of the wax in the ink in the present invention is preferably 30 ≦ x / w ≦ 500. If the ratio is within this range, the amount of solvent surrounding the wax particles is not excessive and insufficient, and sufficient storage stability and ejection stability can be obtained.
In the case of x / w <30, the storage stability is lowered, and there is a possibility that ejection failure may occur due to the deposition of wax at the nozzle opening. In the case of 500 <x / w, since the wax dispersed in the ink is dissolved in the solvent, there is a possibility that ejection failure may occur due to increase in viscosity and storage stability may be lowered.

-Polyether-modified siloxane compound-
As the ink material used in the present invention, a polyether-modified siloxane compound which is a surfactant can also be used. As a result, the ink becomes hard to get wet with the ink repellent layer of the head nozzle plate, and ejection failure due to ink nozzle adhesion is prevented and ejection stability is improved. In addition, the ink hardly adheres to the surface of the nozzle ink repellent layer, which is particularly problematic, and the ink does not easily cause ejection failure.
Among these, those represented by the following general formula (6) to general formula (9) are preferable, and the dynamic surface tension is particularly low without impairing the dispersion stability depending on the type of the water-dispersible color material or the combination of organic solvents. Those having high permeability and leveling properties are preferred.
These polyether-modified siloxane compounds may be used alone or in combination of two or more.
(In the general formula (6), R5 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, m is an integer of 0 to 23, n is an integer of 1 to 10, a is an integer of 1 to 23, b represents an integer of 0 to 23.)

Examples of the compound represented by the general formula (6) include compounds of the following formulas (6-1) to (6-8).

(In said general formula (7), R6 and R7 represent a hydrogen atom or a C1-C4 alkyl group, m is an integer of 1-8, c and d represent an integer of 1-10.)

Examples of the compound represented by the general formula (7) include a compound of the following formula (7-1).

(In said general formula (8), R8 represents a hydrogen atom or a C1-C4 alkyl group, and e represents the integer of 1-8.)

Examples of the compound represented by the general formula (8) include a compound of the following formula (8-1).

[In said general formula (9), R9 represents the polyether group of the following general formula (A), and f represents the integer of 1-8. ]
(In the general formula (A), R10 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, g represents an integer of 0 to 23, and h represents an integer of 0 to 23, provided that g and h are Except when 0 at the same time.)

Examples of the compound represented by the general formula (9) include compounds of the following formulas (9-1) to (9-3).

  Furthermore, as a commercially available polyether-modified siloxane compound surfactant exhibiting the same effect as the above-mentioned compounds, 71ADDITIVE, 74ADDITIVE, 57ADDITIVE, 8029ADDITIVE, 8011ADDITIVE, 8211ADDITIVE, 8019ADDITIVE, 8526ZDIFIVE, 8526Z 2123, FZ-2191, manufactured by Momentive Performance Materials, TSF4440, TSF4441, TSF4445, TSF4446, TSF4450, TSF4452, TSF4460, manufactured by Nissin Chemical Industry, Sylface SAG002, Sylface SAG003, Sylface SAG005 Silface SAG503A, Silface SAG0 8, Sylface SJM003, manufactured by Evonik, TEGO Wet KL245, TEGO Wet 250, TEGO Wet 260, TEGO Wet 265, TEGO Wet 270, TEGO Wet 280, BYK-Japan, BYK-345, BYK-347, BYK-348, BYK-375, BYK-377, etc. are mentioned.

  Moreover, you may use together the said polyether modified siloxane compound and a fluorine-type surfactant, a silicone type surfactant, acetylene glycol, or an acetylene alcohol type surfactant as needed.

  The content of the polyether-modified siloxane compound in the ink is preferably 0.001 to 5% by mass, and more preferably 0.5 to 3% by mass. If it is 0.001 mass% or more, the addition effect of surfactant will be acquired. However, if it exceeds 5 masses, the effect of addition is saturated, so there is no point in increasing the amount.

-Other ingredients-
In addition to the above components, various known additives may be added to the ink of the present invention as necessary. Examples include penetrants, foam suppressors (antifoaming agents), water dispersible resins, pH adjusters, antiseptic / antifungal agents, chelating reagents, rust preventives, antioxidants, UV absorbers, oxygen absorbers, Examples thereof include light stabilizers.

-Foam suppressant-
The antifoaming agent is used to suppress the foaming by adding a small amount to the ink. Here, foaming means that the liquid becomes a thin film and wraps air. Properties such as the surface tension and viscosity of the ink are involved in the generation of the bubbles. That is, a liquid having a high surface tension such as water is difficult to foam because of a force that attempts to reduce the surface area of the liquid as much as possible. On the other hand, highly viscous and highly permeable inks tend to foam due to their low surface tension, and bubbles generated by the viscosity of the solution are easily maintained and are difficult to defoam.

  Usually, the foam suppressor destroys the foam by locally lowering the surface tension of the foam film to destroy the foam, or by interspersing the foam suppressor with a foam suppressor insoluble in the foam liquid. When a polyether-modified siloxane compound surfactant that has a very strong function to lower the surface tension as a surfactant is used in the ink, the surface tension of the foam film is locally controlled even if the former mechanism is used. It cannot be reduced. Therefore, an antifoaming agent that is insoluble in the latter foaming liquid is used. In this case, the stability of the ink is lowered by the antifoaming agent insoluble in the solution.

On the other hand, the foam suppressor represented by the following general formula (10) is not as strong as the polyether-modified siloxane compound surfactant in reducing the surface tension, but has high compatibility with the surfactant. For this reason, it is considered that the foam suppressor is efficiently taken into the foam film, the surface of the foam film is locally unbalanced due to the difference in surface tension between the surfactant and the foam suppressor, and the foam is destroyed. It is done.
(In the general formula (10), R11 and R14 each independently represents an alkyl group having 3 to 6 carbon atoms, R12 and R13 each independently represents an alkyl group having 1 to 2 carbon atoms, and n Represents an integer of 1 to 6.)

  Preferable examples of the compound represented by the general formula (10) include 2,4,7,9-tetramethyldecane-4,7-diol, 2,5,8,11-tetramethyldodecane-5,8. -Diols. 2,5,8,11-tetramethyldodecane-5,8-diol is particularly preferred because of its high antifoaming effect and high compatibility with ink.

  The content of the foam suppressor in the ink is preferably 0.01 to 10% by mass, and more preferably 0.1 to 5% by mass. When the content is 0.01% by mass, a foam suppression effect is obtained. When the content is 10% by mass or less, the foam suppression effect reaches its peak, and ink physical properties such as viscosity and particle size are adversely affected. There is nothing wrong.

-Water dispersible resin-
Water-dispersible resins that have excellent film-forming properties (image formability) and high water repellency, high water resistance, and high weather resistance are highly water resistant and have high image density (high color development). Useful for recording, and examples thereof include condensation-type synthetic resins, addition-type synthetic resins, and natural polymer compounds.
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 fluorine-based resin. Examples of the addition type 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 rubber.
Among these, acryl-silicone resin fine particles and fluorine-based resin fine particles are particularly preferable. Two or more kinds of the water dispersible resins may be used in combination.

As the water-dispersible resin, a resin itself having a hydrophilic group and having a self-dispersibility, or a resin itself having no dispersibility and imparted with a surfactant or a resin having a hydrophilic group can be used. Among these, an emulsion of resin particles obtained by emulsion and suspension polymerization of an ionomer of a polyester resin or a polyurethane resin or an unsaturated monomer is optimal.
In the case of emulsion polymerization of an unsaturated monomer, the resin emulsion is reacted by reacting in water to which an unsaturated monomer, a polymerization initiator, a surfactant, a chain transfer agent, a chelating agent, and a pH adjusting agent are added. Therefore, a water-dispersible resin can be easily obtained, the resin configuration can be easily changed, and the desired properties can be easily produced.

The water-dispersible resin causes breakage of the molecular chain such as dispersion breakage and hydrolysis under strong alkalinity and strong acidity. Is preferably 4 to 12, more preferably 6 to 11 and even more preferably 7 to 10 from the viewpoint of miscibility with a water-dispersible colorant.
The average particle diameter (D ₅₀ ) of the water-dispersible resin is related to the viscosity of the dispersion, and for the same composition, the viscosity at the same solid content increases as the particle diameter decreases. The average particle diameter (D ₅₀ ) of the water-dispersible resin is preferably 50 nm or more so that the viscosity does not become excessively high when converted into an ink. Further, when the particle size is several tens of μm, it becomes larger than the nozzle opening of the ink jet head and cannot be used. If particles having a large particle diameter are present in the ink even if they are smaller than the nozzle opening, the discharge property is deteriorated. Therefore, the average particle diameter (D ₅₀ ) is more preferably 200 nm or less, and even more preferably 150 nm or less, in order not to inhibit the ink ejection properties.

The water-dispersible resin has a function of fixing a water-dispersible color material on the paper surface, and has a function of forming a film at room temperature to improve the fixability of the color material. Therefore, the minimum film-forming temperature (MFT) of the water-dispersible resin is preferably 30 ° C. or lower. Further, when the glass transition temperature of the water-dispersible resin is −40 ° C. or lower, the viscosity of the resin film becomes strong and the printed matter is tacked. Therefore, the glass transition temperature is preferably −30 ° C. or higher.
The content of the water-dispersible resin in the ink is preferably 0.5 to 10% by mass and more preferably 1 to 8% by mass in terms of solid content.

-PH adjuster-
The pH adjuster is not particularly limited as long as it can adjust the pH to 7 to 11 without adversely affecting the prepared ink, and can be appropriately selected according to the purpose.
Examples thereof include alcohol amines, alkali metal hydroxides, ammonium hydroxides, phosphonium hydroxides, alkali metal carbonates, and the like.
When the pH is out of the range of 7 to 11, the amount of the ink jet head and the ink supply unit that melts out is large, and problems such as ink deterioration, leakage, and ejection failure may occur.
Examples of the alcohol amines include diethanolamine, triethanolamine, 2-amino-2-ethyl-1,3-propanediol, and the like.
Examples of the alkali metal hydroxide include lithium hydroxide, sodium hydroxide, and potassium hydroxide.
Examples of the ammonium hydroxide include ammonium hydroxide and quaternary ammonium hydroxide.
Examples of the phosphonium hydroxide include quaternary phosphonium hydroxide.
Examples of the alkali metal carbonate include lithium carbonate, sodium carbonate, and potassium carbonate.

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

-Chelating reagent-
Examples of the chelating reagent include sodium ethylenediaminetetraacetate, sodium nitrilotriacetate, sodium hydroxyethylethylenediaminetriacetate, sodium diethylenetriaminepentaacetate, sodium uramil diacetate, and the like.

-Antirust agent-
Examples of the rust inhibitor include acidic sulfite, sodium thiosulfate, ammonium thiodiglycolate, diisopropylammonium nitrite, pentaerythritol tetranitrate, and dicyclohexylammonium nitrite.

-Antioxidant-
Examples of the antioxidant include phenolic antioxidants (including hindered phenolic antioxidants), amine antioxidants, sulfurous antioxidants, phosphorus antioxidants, and the like.

-UV absorber-
Examples of the ultraviolet absorber include a benzophenone ultraviolet absorber, a benzotriazole ultraviolet absorber, a salicylate ultraviolet absorber, a cyanoacrylate ultraviolet absorber, and a nickel complex ultraviolet absorber.

-Manufacture of ink-
The ink used in the present invention is produced by dispersing or dissolving a coloring material, an organic solvent X, water, a copolymer, and other components added as necessary in an aqueous medium, and further stirring and mixing as necessary. . This stirring and mixing can be performed by, for example, a sand mill, a homogenizer, a ball mill, a paint shaker, an ultrasonic disperser, and the like. The stirring and mixing is performed by a stirrer using a normal stirring blade, a magnetic stirrer, a high-speed disperser, or the like. be able to.
Further, the copolymer having the structural unit represented by the general formula (1) in the present invention is not particularly limited, but can be added as a dispersant for dispersing the coloring material in an aqueous medium, A water-dispersible resin can also be added to the ink in the form of a water dispersion.

-Ink physical properties-
The physical properties of the ink used in the present invention are not particularly limited and can be appropriately selected according to the purpose.
However, when the static surface tension of the ink is 20 mN / m or more and the dynamic surface tension at the bubble life time of 15 msec by the maximum bubble pressure method is 34 mN / m or less, sufficient wettability is secured to the recording medium. In spite of being able to do so, it becomes difficult to get wet with the water repellent film of the nozzle plate optool of the ink jet head, and it is preferable because it is possible to secure the discharge stability and make the ink extremely stable.
The viscosity of the ink at 25 ° C. is preferably 5 to 25 mPa · s, more preferably 6 to 20 mPa · s. If it is 5 mPa · s or more, the effect of improving the printing density and the character quality can be obtained. Moreover, if it is 25 mPa * s or less, ink discharge property is securable.
The viscosity can be measured at 25 ° C. using, for example, a viscometer (RE-550L, manufactured by Toki Sangyo Co., Ltd.).

The ink discharge device according to the present invention uses the piezoelectric element as a pressure generating means for pressurizing the ink in the ink flow path as the ink discharge head, and deforms the diaphragm that forms the wall surface of the ink flow path to A so-called piezo type that discharges ink droplets by changing the temperature (see Japanese Patent Application Laid-Open No. 2-51734), or a so-called thermal type that generates bubbles by heating ink in an ink flow path using a heating resistor. (Refer to Japanese Patent Laid-Open No. 61-59911), the diaphragm and the electrode forming the wall surface of the ink flow path are arranged to face each other, and the diaphragm is deformed by the electrostatic force generated between the diaphragm and the electrode. Thus, any ink discharge head such as an electrostatic type (see JP-A-6-71882) that discharges ink droplets by changing the volume in the ink flow path can be mounted. That.
In the present invention, the ink may be stored in an ink storage container such as an ink cartridge.

<Recording medium>
There is no particular limitation on the recording medium on which recording can be performed using the ink ejection apparatus of the present invention, and it can be selected as appropriate according to the purpose. , OHP sheets, and general-purpose printing paper. However, the ink ejection apparatus of the present invention is very excellent in that good recording can be performed on commercial printing paper as well as other paper.
Commercial printing paper as used herein refers to printing paper having a coating layer on at least one surface of the support. For example, printing paper using a filler such as calcium carbonate or kaolin as the coating layer material is used. Can be mentioned. Moreover, as for the coated paper which is an example of commercial printing paper, the coating layer is made of white pigments such as clay (kaolin) and calcium carbonate, and an adhesive (binder) such as starch.
The recorded matter having an image formed by using the ink ejection apparatus of the present invention has high image quality, no bleeding, excellent temporal stability, and is suitably used for various applications as a material on which various prints or images are recorded can do.

Among recording media, liquid absorption characteristics are in a certain range because images with excellent image quality (image density, saturation, beading, color bleed), high gloss, and smear fixability can be recorded. The internal recording medium is suitable. Specific examples include commercial printing paper having a coating layer on at least one surface of a support, and pure water at a contact time of 100 ms as measured by a dynamic scanning absorption meter on the surface having the coating layer. the transfer amount of the printing paper is 2~35mL / m ^2, and the printing paper the transfer amount of the printing paper of the pure water is 3~40mL / m ² at a contact time of 400ms are preferred. If the transfer amount of pure water is less than this, beading (a phenomenon in which adjacent dots are attracted and the image has a rough feeling) and color bleeding (bleeding between colors) are likely to occur. In some cases, if the transfer amount of pure water is too large, the ink dot diameter after recording is smaller than the desired diameter and the solid image may not be filled.

The transfer amount of pure water can be measured using a dynamic scanning absorption meter (K350 series D type, manufactured by Kyowa Seiko Co., Ltd.). The transfer amount at the contact time of 100 ms can be obtained by interpolation from the measured value of the transfer amount at the contact time adjacent to the contact time.
Examples of commercially available printing paper having liquid absorption characteristics within the above-mentioned range include, for example, POD gloss coat, OK top coat +, OK Kanto +, SA Kanto + (manufactured by Oji Paper Co., Ltd.), Super MIdal, Aurora Coat, Space DX (manufactured by Nippon Paper Industries Co., Ltd.), α mat, mu coat (manufactured by Hokuetsu Paper Co., Ltd.), thunderbird art, thunderbird super art (manufactured by Chuetsu Pulp Co., Ltd.), pearl coat N (manufactured by Mitsubishi Paper Industries), and the like.

<Ink Ejecting Device, Ink Ejecting Method>
The ink ejection apparatus of the present invention can be suitably used for various recording apparatuses using an ink jet recording system, such as a printer, a facsimile apparatus, a copying apparatus, a printer / fax / copier complex machine, and a three-dimensional modeling apparatus.
In the present invention, the ink ejection apparatus and the ink ejection method are an apparatus capable of ejecting ink, various processing liquids, and the like onto a recording medium, and a method of performing recording using the apparatus. The recording medium means a medium on which ink or various processing liquids can be temporarily attached.
The ink ejection apparatus of the present invention includes the ink, a nozzle that ejects the ink, a plurality of individual liquid chambers that communicate with the nozzle, an inflow channel that allows the ink to flow into the individual liquid chamber, and the ink as the individual liquid. An ink discharge head having an outflow channel for allowing the ink to flow out of the chamber, wherein the ink flowing out from the outflow channel flows into the inflow channel and circulates, and the ink is supplied to the individual liquid chamber. An ink discharge apparatus having a circulation-type discharge head, having negative pressure generating means for generating a negative pressure that flows out from the nozzle.
The ink ejection method of the present invention includes the ink, a nozzle that ejects the ink, a plurality of individual liquid chambers that communicate with the nozzle, an inflow channel that allows the ink to flow into the individual liquid chamber, and the ink as the individual liquid. An ink discharge head having an outflow channel for flowing out of the chamber, and the ink discharged from the outflow channel is circulated by flowing the ink into the inflow channel, and the individual liquid A negative pressure generating step for generating a negative pressure to flow out of the chamber;

The ink ejection device includes not only a head portion that ejects ink but also means for feeding, transporting, and ejecting the recording medium, and other devices called pre-processing devices and post-processing devices. it can.
The ink discharge apparatus and the ink discharge method may include a heating unit used in the heating step and a drying unit used in the drying step. The heating means and the drying means include, for example, a means for heating and drying the printing surface and the back surface of the recording medium. Although it does not specifically limit as a heating means and a drying means, For example, a warm 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 ink ejecting apparatus and the ink ejecting method are not limited to those in which significant images such as characters and figures are visualized by ink. For example, what forms patterns, such as a geometric pattern, etc. includes what forms a three-dimensional image.
In addition, the ink discharge 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 limited, and a circulation type discharge head that circulates ink in a plurality of individual liquid chambers. Is used. The circulation type discharge head will be described later separately.
Further, in this ink ejection apparatus, not only a desktop type but also a wide recording apparatus that can print on an A0 size recording medium, or continuous paper wound up in a roll shape, for example, is used as the recording medium. Possible continuous paper printers are also included.

An example of the ink ejection device will be described with reference to FIGS. FIG. 1 is a perspective view of the apparatus. FIG. 2 is an explanatory perspective view of a main tank for storing ink. An image forming apparatus 400 as an example of an ink ejection apparatus is a serial type image forming apparatus. A mechanism unit 420 is provided in the exterior 401 of the image forming apparatus 400. Each ink storage portion 411 of the main tank 410 (410k, 410c, 410m, 410y) for each color of black (K), cyan (C), magenta (M), yellow (Y) is packaged, for example, an aluminum laminate film It is formed by a member. The ink storage unit 411 is stored 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 on the inner side of the opening when the cover 401c of the apparatus main body is opened. A main tank 410 is detachably attached to the cartridge holder 404. Thus, the ink discharge ports 413 of the main tank 410 and the discharge heads 434 for the respective colors communicate with each other via the supply tubes 436 for the respective colors, and ink can be discharged from the discharge heads 434 to the recording medium.

<Ink Ejection Device and Ink Ejection Method Having Circulation Type Ejection Head>
An example of the circulation type discharge head will be described below with reference to FIGS. FIG. 3 is an external perspective view of the ink discharge head, FIG. 4 is a cross-sectional explanatory view in a direction orthogonal to the nozzle arrangement direction of the head, and FIG. 6 is an explanatory plan view of the nozzle plate of the head, FIG. 7 is an explanatory plan view of each member constituting the flow path member of the head, and FIG. 8 is an explanatory plan view of each member constituting the common liquid chamber member of the head. It is.

In this ink discharge head, a nozzle plate 1, a flow path plate 2, and a vibration plate member 3 as a wall surface member are laminated and joined. A piezoelectric actuator 11 that displaces the diaphragm member 3, a common liquid chamber member 20, and a cover 29 are provided.
The nozzle plate 1 has a plurality of nozzles 4 that eject ink.
The flow path plate 2 forms an individual liquid chamber 6 that communicates with the nozzle 4, a fluid resistance portion 7 that communicates with the individual liquid chamber 6, and a liquid introduction portion 8 that communicates with the fluid resistance portion 7. The flow path plate 2 is formed by laminating and joining a plurality of plate-like members 41 to 45 from the nozzle plate 1 side, and laminating and joining these plate-like members 41 to 45 and the vibration plate member 3. A member 40 is configured.
The diaphragm member 3 has a filter portion 9 as an opening through the liquid introduction portion 8 and the common liquid chamber 10 formed by the common liquid chamber member 20.
The inflow channel may be a channel connected to the individual liquid chamber 6 and may be a channel in front of the individual liquid chamber inflow, and the liquid introduction part 8 and the common liquid chamber 10 correspond to the inflow channel. To do.
The diaphragm member 3 is a wall surface member that forms the wall surface of the individual liquid chamber 6 of the flow path plate 2. The diaphragm member 3 has a two-layer structure (not limited), and is formed of a first layer that forms a thin portion and a second layer that forms a thick portion from the flow path plate 2 side. A deformable vibration region 30 is formed in a portion corresponding to the chamber 6.

Here, as shown in FIG. 6, a plurality of nozzles 4 are arranged in a staggered pattern on the nozzle plate 1.
As shown in FIG. 7A, the plate-like member 41 constituting the flow path plate 2 includes a through groove portion (meaning a groove-shaped through hole) 6a constituting the individual liquid chamber 6, a fluid resistance portion 51, Through groove portions 51 a and 52 a constituting the circulation flow path 52 are formed.
Similarly, as shown in FIG. 7B, the plate-like member 42 is formed with a through groove portion 6 b constituting the individual liquid chamber 6 and a through groove portion 52 b constituting the circulation channel 52.
Similarly, as shown in FIG. 7C, the plate-like member 43 is formed with a through groove portion 6 c constituting the individual liquid chamber 6 and a through groove portion 53 a having the nozzle arrangement direction constituting the circulation flow channel 53 as a longitudinal direction. Has been. Similarly, as shown in FIG. 7 (d), the plate-like member 44 has a through groove portion 6 d constituting the individual liquid chamber 6, a through groove portion 7 a constituting the fluid resistance portion 7, and a through portion constituting the liquid introduction portion 8. A groove 8 a and a through groove 53 b whose longitudinal direction is the nozzle arrangement direction that constitutes the circulation channel 53 are formed.
Similarly, as shown in FIG. 7 (e), the plate-like member 45 includes a through groove portion 6 e constituting the individual liquid chamber 6 and a through groove portion 8 b (filter) having the nozzle arrangement direction constituting the liquid introduction portion 8 as a longitudinal direction. And a through-groove portion 53c having a nozzle arrangement direction constituting the circulation flow path 53 as a longitudinal direction.

As shown in FIG. 7 (f), the diaphragm member 3 is formed with a vibration region 30, a filter portion 9, and a through groove portion 53 d whose longitudinal direction is the nozzle arrangement direction constituting the circulation flow path 53. .
Thus, a complicated flow path can be formed with a simple configuration by configuring the flow path member by laminating and joining a plurality of plate-like members.
With the above configuration, the flow path member 40 including the flow path plate 2 and the vibration plate member 3 includes the fluid resistance portion 51, the circulation flow path 52, and the circulation along the surface direction of the flow path plate 2 leading to each individual liquid chamber 6. A circulation channel 53 in the thickness direction of the channel member 40 that communicates with the channel 52 is formed. The circulation channel 53 communicates with a circulation common liquid chamber 50 described later.
The outflow channel may be a channel connected to the individual liquid chamber 6 and a channel after “inflow” of the individual liquid chamber, and the circulation channels 52 and 53 and the circulation common liquid chamber 50 are outflow. Corresponds to the road.

On the other hand, the common liquid chamber member 20 is formed with a common liquid chamber 10 to which ink is supplied from a supply / circulation mechanism 494 and a circulation common liquid chamber 50.
As shown in FIG. 8A, the first common liquid chamber member 21 constituting the common liquid chamber member 20 includes a piezoelectric actuator through hole 25a, a through groove portion 10a serving as a downstream common liquid chamber 10A, and a circulation. A groove portion 50 a having a bottom that becomes the common liquid chamber 50 is formed.
Similarly, as shown in FIG. 8B, the second common liquid chamber member 22 is formed with a piezoelectric actuator through hole 25b and a groove portion 10b serving as the upstream common liquid chamber 10B.
Referring also to FIG. 3, the second common liquid chamber member 22 has a through hole 71 a serving as a supply port portion through one end portion of the common liquid chamber 10 in the nozzle arrangement direction and the supply port 71.
Similarly, the first common liquid chamber member 21 and the second common liquid chamber member 22 are provided with the other end of the circulation common liquid chamber 50 in the nozzle arrangement direction (the end opposite to the through hole 71a) and the circulation port 81. Through holes 81a and 81b are formed.
In addition, in FIG. 8, the groove part with the bottom is shown with surface coating (the same applies to the following drawings).
As described above, the common liquid chamber member 20 is constituted by the first common liquid chamber member 21 and the second common liquid chamber member 22, and the first common liquid chamber member 21 is joined to the diaphragm member 3 side of the flow path member 40. Then, the second common liquid chamber member 22 is laminated and joined to the first common liquid chamber member 21.

Here, the first common liquid chamber member 21 forms a downstream common liquid chamber 10 </ b> A that is a part of the common liquid chamber 10 that communicates with the liquid introduction unit 8, and a circulation common liquid chamber 50 that communicates with the circulation channel 53. ing. The second common liquid chamber member 22 forms an upstream common liquid chamber 10 </ b> B that is the remaining part of the common liquid chamber 10.
At this time, the downstream common liquid chamber 10A, which is a part of the common liquid chamber 10, and the circulating common liquid chamber 50 are arranged side by side in a direction orthogonal to the nozzle arrangement direction, and the circulating common liquid chamber 50 is arranged in the common liquid chamber 10. It is arranged at the position projected inside.
Thereby, the dimension of the circulation common liquid chamber 50 is not restricted by the dimension required for the flow path including the individual liquid chamber 6, the fluid resistance portion 7 and the liquid introduction portion 8 formed by the flow path member 40.
The circulation common liquid chamber 50 and a part of the common liquid chamber 10 are arranged side by side, and the circulation common liquid chamber 50 is arranged at a position projected into the common liquid chamber 10, thereby orthogonal to the nozzle arrangement direction. The width of the head in the direction can be suppressed, and the enlargement of the head can be suppressed. The common liquid chamber member 20 forms a common liquid chamber 10 and a circulation common liquid chamber 50 to which ink is supplied from a head tank or an ink cartridge.

On the other hand, a piezoelectric actuator 11 including an electromechanical conversion element as a driving unit that deforms the vibration region 30 of the diaphragm member 3 is disposed on the opposite side of the diaphragm member 3 from the individual liquid chamber 6.
As shown in FIG. 5, the piezoelectric actuator 11 has a piezoelectric member 12 bonded on a base member 13, and the piezoelectric member 12 is grooved by half-cut dicing so that a required number of piezoelectric members 12 is provided. The columnar piezoelectric elements 12A and 12B are formed in a comb shape at a predetermined interval.
Here, the piezoelectric element 12A of the piezoelectric member 12 is a piezoelectric element that is driven by giving a drive waveform, and the piezoelectric element 12B is used as a mere support without giving a drive waveform. However, all the piezoelectric elements 12A and 12B are driven. It can also be used as a piezoelectric element.
The piezoelectric element 12 </ b> A is joined to a convex portion 30 a that is an island-shaped thick portion formed in the vibration region 30 of the diaphragm member 3. Further, the piezoelectric element 12 </ b> B is joined to the convex portion 30 b which is a thick portion of the diaphragm member 3.

The piezoelectric member 12 is formed by alternately laminating piezoelectric layers and internal electrodes. The internal electrodes are drawn out to end faces, external electrodes are provided, and the flexible wiring member 15 is connected to the external electrodes.
In the circulation type discharge head configured as described above, for example, by lowering the voltage applied to the piezoelectric element 12A from the reference potential, the piezoelectric element 12A contracts, and the vibration region 30 of the vibration plate member 3 descends, so that the individual liquid chamber 6 As the volume expands, the ink flows into the individual liquid chamber 6.
Thereafter, the voltage applied to the piezoelectric element 12A is increased to extend the piezoelectric element 12A in the stacking direction, and the vibration region 30 of the diaphragm member 3 is deformed in the direction toward the nozzle 4 to contract the volume of the individual liquid chamber 6. As a result, the ink in the individual liquid chamber 6 is pressurized, and the ink is ejected from the nozzle 4.
Then, by returning the voltage applied to the piezoelectric element 12A to the reference potential, the vibration region 30 of the diaphragm member 3 is restored to the initial position, and the individual liquid chamber 6 expands to generate a negative pressure. Ink is filled into the individual liquid chamber 6 from the chamber 10. Therefore, after the vibration of the meniscus surface of the nozzle 4 is attenuated and stabilized, the operation for the next discharge is started.

  Note that the driving method of the head is not limited to the above example (pulling-pushing), and it is also possible to perform striking or pushing depending on the direction to which the driving waveform is given. In the above-described embodiment, the laminated piezoelectric element is described as the pressure generating means for applying the pressure fluctuation to the individual liquid chamber 6, but the present invention is not limited to this, and a thin film piezoelectric element can also be used. . Furthermore, a heating resistor can be provided in the individual liquid chamber 6 to generate a bubble by generating heat by generating heat from the heating resistor, or to generate a pressure variation using electrostatic force. .

Next, an example of an ink circulation system using a circulation type discharge head will be described with reference to FIG.
FIG. 9 is a block diagram showing the ink circulation system.
As shown in FIG. 9, the ink circulation system includes a main tank, an ink discharge head, a supply tank, a circulation tank, a compressor, a vacuum pump, a first liquid feed pump, a second liquid feed pump, a regulator (R), and a supply side pressure. It consists of a sensor, a circulation side pressure sensor, and the like. The vacuum pump corresponds to a means for generating a negative pressure. The supply side pressure sensor is connected between the supply tank and the ink discharge head and on the supply flow path side connected to the supply port 71 (see FIG. 3) of the ink discharge head. The circulation-side pressure sensor is connected between the ink discharge head and the circulation tank and on the circulation flow path side connected to the circulation port 81 (see FIG. 3) of the ink discharge head.

One of the circulation tanks is connected to the supply tank via a first liquid feed pump, and the other of the circulation tanks is connected to the main tank via a second liquid feed pump. As a result, ink flows from the supply tank through the supply port 71 into the ink discharge head, is discharged from the circulation port, is discharged to the circulation tank, and is further sent from the circulation tank to the supply tank by the first liquid feed pump. The ink circulates.
In addition, a compressor is connected to the supply tank, and the supply side pressure sensor is controlled to detect a predetermined positive pressure. On the other hand, a vacuum pump is connected to the circulation tank, and control is performed so that a predetermined negative pressure is detected by the circulation side pressure sensor. Thereby, the negative pressure of the meniscus can be kept constant while circulating the ink through the ink ejection head.
In addition, when droplets are ejected from the nozzles of the circulation type discharge head, the amount of ink in the supply tank and the circulation tank decreases. It is desirable to replenish ink. The timing of ink replenishment from the main tank to the circulation tank depends on the detection result of the liquid level sensor provided in the circulation tank, such as when the ink level in the circulation tank falls below a predetermined level. Can be controlled.

Next, ink circulation in the circulation type discharge head will be described. As shown in FIG. 3, a supply port 71 that communicates with the common liquid chamber and a circulation port 81 that communicates with the circulation common liquid chamber 50 are formed at the end of the common liquid chamber member 20. The supply port 71 and the circulation port 81 are connected to a supply tank / circulation tank (see FIG. 9) for storing ink via tubes. Then, the ink stored in the supply tank is supplied to the individual liquid chamber 6 through the supply port 71, the common liquid chamber 10, the liquid introducing portion 8, and the fluid resistance portion 7.
Furthermore, while the ink in the individual liquid chamber 6 is ejected from the nozzle 4 by driving the piezoelectric element 12, a part or all of the ink remaining in the individual liquid chamber 6 without being ejected is circulated in the fluid resistance portion 51. It is circulated to the circulation tank through the flow paths 52 and 53, the circulation common liquid chamber 50, and the circulation port 81.

  The ink circulation can be performed not only when the circulation type discharge head is operated but also when the operation is stopped. By circulating at the time of operation stop, the ink in the individual liquid chamber is always refreshed, and aggregation and sedimentation of components contained in the ink can be suppressed, which is preferable. On the other hand, a vacuum pump is connected to the circulation tank in order to keep the meniscus negative pressure constant, but when highly volatile components are contained in the ink, it gradually volatilizes and the composition of the ink is reduced. There is also a problem that it varies over time. In particular, when an aqueous pigment ink containing an organic solvent (organic solvent X) having an SP value of 8.9 to 12.0 used in the present invention is used, volatile components such as moisture and compound Z contained in the ink are volatilized. As a result, the ink changes to a hydrophobic composition. As the balance between hydrophilicity and hydrophobicity changes in this way, the dispersion stability of the pigment contained in the ink is impaired, and there is a problem that ejection disturbance is likely to occur when printing continuously. Even in the case of a composition having high hydrophobicity, good dispersion stability can be maintained. By using the ink of the present invention, a high-quality image with less image defects such as ejection disturbance even when combined with a circulation head is used. It can be obtained with productivity.

Next, an example of an apparatus for ejecting ink using a circulation-type ejection head will be described with reference to FIGS. FIG. 10 is an explanatory plan view of the main part of the apparatus, and FIG.
This apparatus is a serial type apparatus, and the carriage 403 reciprocates in the main scanning direction by the main scanning moving mechanism 493. The main scanning movement mechanism 493 includes a guide member 401, a main scanning motor 405, a timing belt 408, and the like. The guide member 401 spans the left and right side plates 491A and 491B and holds the carriage 403 so as to be movable. The carriage 403 is reciprocated in the main scanning direction by the main scanning motor 405 via the timing belt 408 spanned between the driving pulley 406 and the driven pulley 407.
An ink discharge unit 440 having an ink discharge head 404 is mounted on the carriage 403. The ink discharge head 404 of the ink discharge unit 440 discharges, for example, yellow (Y), cyan (C), magenta (M), and black (K) inks. The ink ejection head 404 is mounted with a nozzle row composed of a plurality of nozzles arranged in the sub-scanning direction orthogonal to the main scanning direction and the ejection direction facing downward.

  Ink is supplied and circulated in the ink discharge head 404 by a supply / circulation mechanism 494 for supplying ink stored outside the ink discharge head 404 to the ink discharge head 404. In this example, the supply / circulation mechanism 494 includes a supply tank, a circulation tank, a compressor, a vacuum pump, a liquid feed pump, a regulator (R), and the like. The supply-side pressure sensor is connected between the supply tank and the ink discharge head and on the supply flow path side connected to the supply port 71 of the ink discharge head. The circulation side pressure sensor is connected between the ink discharge head and the circulation tank and on the circulation flow path side connected to the circulation port 81 of the ink discharge head.

This apparatus includes a transport mechanism 495 for transporting the paper 410. The transport mechanism 495 includes a transport belt 412 serving as transport means, and a sub-scanning motor 416 for driving the transport belt 412.
The conveyance belt 412 adsorbs the paper 410 and conveys it at a position facing the ink ejection head 404. The transport belt 412 is an endless belt and is stretched between the transport roller 413 and the tension roller 414. The adsorption can be performed by electrostatic adsorption or air suction.
The transport belt 412 rotates in the sub-scanning direction when the transport roller 413 is rotationally driven by the sub-scanning motor 416 via the timing belt 417 and the timing pulley 418.

Further, a maintenance / recovery mechanism 420 that performs maintenance / recovery of the ink ejection head 404 is disposed on the side of the conveyance belt 412 on one side of the carriage 403 in the main scanning direction.
The maintenance / recovery mechanism 420 includes, for example, a cap member 421 for capping the nozzle surface (surface on which the nozzle is formed) of the ink discharge head 404, a wiper member 422 for wiping the nozzle surface, and the like.
The main scanning movement mechanism 493, the supply / circulation mechanism 494, the maintenance / recovery mechanism 420, and the transport mechanism 495 are attached to a housing including the side plates 491A and 491B and the back plate 491C.
In this apparatus configured as described above, the paper 410 is fed and sucked onto the transport belt 412, and the paper 410 is transported in the sub-scanning direction by the circular movement of the transport belt 412.
Therefore, by driving the ink discharge head 404 according to the image signal while moving the carriage 403 in the main scanning direction, ink is discharged onto the stopped paper 410 to form an image.
As described above, since this apparatus includes the circulation type discharge head, a high-quality image can be stably formed.

Next, another example of the ink discharge unit will be described with reference to FIG. FIG. 12 is an explanatory plan view of the main part of the unit.
The ink discharge unit includes a casing portion composed of side plates 491A and 491B and a back plate 491C, a main scanning movement mechanism 493, a carriage 403, and an ink among members constituting the ink discharge device. The discharge head 404 is configured.
An ink discharge unit in which at least one of the above-described maintenance / recovery mechanism 420 and supply / circulation mechanism 494 is further attached to, for example, the side plate 491B of the ink discharge unit may be configured.
In the present application, an “ink ejection head” is a functional component that ejects and ejects ink from nozzles.

  As an energy generation source for ejecting ink, piezoelectric actuators (laminated piezoelectric elements and thin film piezoelectric elements), thermal actuators using electrothermal transducers such as heating resistors, electrostatic actuators consisting of diaphragms and counter electrodes are used. To be included.

The “ink ejection unit” is an assembly of functional parts and mechanisms integrated with an ink ejection head, and is an assembly of parts related to ink ejection. For example, the “ink discharge unit” includes a combination of at least one of a supply / circulation mechanism, a carriage, a maintenance / recovery mechanism, and a main scanning movement mechanism with an ink discharge head.
Here, the term “integration” refers to, for example, an ink discharge head, a functional component, and a mechanism that are fixed to each other by fastening, adhesion, engagement, etc., and one in which one is held movably with respect to the other. Including. Further, the ink discharge head, the functional component, and the mechanism may be configured to be detachable from each other.
For example, there is an ink discharge unit in which an ink discharge head and a supply / circulation mechanism are integrated. Also, there are some in which the ink discharge head and the supply / circulation mechanism are integrated by being connected to each other by a tube or the like. Here, a unit including a filter may be added between the supply / circulation mechanism of these ink discharge units and the ink discharge head.
Some ink discharge units are integrated with an ink discharge head and a carriage.
In some ink discharge units, the ink discharge head and the scanning movement mechanism are integrated by holding the ink discharge head movably on a guide member constituting a part of the scanning movement mechanism.
Also, there is an ink discharge unit in which a cap member that is a part of a maintenance / recovery mechanism is fixed to a carriage to which the ink discharge head is attached, and the ink discharge head, the carriage, and the maintenance / recovery mechanism are integrated. .
Some ink discharge units have an ink discharge head and a supply mechanism integrated by connecting a tube to an ink discharge head to which a supply / circulation mechanism or a flow path component is attached. The ink from the ink storage source is supplied to the ink discharge head via this tube.
The main scanning movement mechanism includes a guide member alone. The supply mechanism includes a single tube and a single loading unit.

In the present application, an “ink discharge device” is a device that includes an ink discharge head or an ink discharge unit and drives the ink discharge head to discharge ink. The ink ejection device includes not only a device capable of ejecting ink to an object to which ink can adhere, but also a device that ejects ink toward the air or liquid.
The “ink discharge device” may include means for feeding, transporting, and discharging a material to which ink can be attached, a pre-processing device, a post-processing device, and the like.
For example, as an “ink ejection device”, an image forming device that is a device that ejects ink to form an image on paper, a powder in which powder is formed in a layer to form a three-dimensional model (three-dimensional model) There is a three-dimensional modeling apparatus (three-dimensional modeling apparatus) that discharges ink to a body layer.
Further, the “ink ejecting apparatus” is not limited to an apparatus in which significant images such as characters and figures are visualized by ejected ink. For example, what forms a pattern etc. which does not have a meaning in itself, and what forms a three-dimensional image are also included.

In addition, the “ink discharge device” includes a device in which the ink discharge head and the device to which the ink can be attached move relatively, but is not limited thereto. Specific examples include a serial type device that moves the ink discharge head, a line type device that does not move the ink discharge head, and the like.
In addition, the terms “image formation”, “recording”, “printing”, “printing”, “printing”, “modeling” and the like in the terms of the present application are all synonymous.

-Heat drying means, heat drying process-
The ink discharge apparatus of the present invention may have a heat drying means as necessary, and a heat drying process can be provided after the ink discharge process. For example, an infrared drying apparatus, a microwave drying apparatus, a roll The recording medium provided with ink can be dried by a heater, a drum heater, hot air, or the like.
Further, the image forming apparatus may include a fixing unit that smoothes the surface of the image or fixes the image, and may be provided with a fixing step of heating to 100 ° C. to 150 ° C. by a heating unit and performing heat fixing. By providing the fixing step, the glossiness and fixing property of the image recorded matter are improved. As the heat fixing means, a roller having a heated mirror surface, a drum heater or the like is preferable, and the mirror surface portion (smooth portion) of the roll heater or drum heater may be brought into contact with the image surface. The heating temperature is preferably a fixing roller heated to 100 to 150 ° C. in consideration of image quality, safety and economy.

An example of the image forming apparatus is shown in FIG.
This figure shows the case of having an image forming process and a drying process. 1 is a recording medium, 2 is an ink ejection unit, 3 is a transport belt, 4 is a hot air drying device, 5 is an image forming unit, and 6 is a drying process. Reference numeral 7 denotes a transfer roll.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited at all by these Examples. In the examples, “parts” and “%” are “parts by mass” and “% by mass” unless otherwise specified.

<Synthesis of copolymer>
[Monomer synthesis]
After 62.0 g (525 mmol) of 1,6-hexanediol (manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in 700 mL of methylene chloride, 20.7 g (262 mmol) of pyridine was added. Next, a solution prepared by dissolving 50.0 g (262 mmol) of 2-naphthalenecarbonyl chloride (manufactured by Tokyo Chemical Industry Co., Ltd.) in 100 mL of methylene chloride was added dropwise with stirring for 2 hours, and then stirred at room temperature for 6 hours. Further, after washing with water, the organic phase was isolated. Next, after drying with magnesium sulfate, the solvent was distilled off. Furthermore, purification was performed 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-hydroxyhexyl ester.
After 42.1 g (155 mmol) of 2-naphthoic acid-2-hydroxyhexyl ester was dissolved in 80 mL of dry methyl ethyl ketone, the temperature was raised to 60 ° C. Next, a solution prepared by dissolving 24.0 g (155 mmol) of Karenz MOI (2-methacryloyloxyethyl isocyanate) (manufactured by Showa Denko KK) in 20 mL of dry methyl ethyl ketone was added dropwise over 1 hour with stirring. Stir at 12 ° C. for 12 hours. Furthermore, after cooling to room temperature, the solvent was distilled off. Next, it is purified by silica gel column chromatography using a mixed solvent of methylene chloride / methanol (volume ratio 99/1) as an eluent, and 57.0 g of [Monomer represented by the following chemical formula (I-1) M-1] was obtained.

[Synthesis of Copolymer R-1]
A monomer solution was prepared by dissolving 3.80 g (52.7 mmol) of acrylic acid (manufactured by Aldrich) and 11.26 g (26.3 mmol) of [monomer M-1] in 75 mL of dry methyl ethyl ketone. After heating 10% of the monomer solution to 75 ° C. under an argon stream, 0.59 g (3.61 mmol) of 2,2′-azoiso (butyronitrile) (manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in the remaining monomer solution. Was added dropwise over 1.5 hours and stirred at 75 ° C. for 4 hours. After cooling to room temperature, the resulting reaction solution was dropped into hexane. The precipitated copolymer was separated by filtration and dried under reduced pressure to obtain 14.55 g of [Copolymer R-1] (weight average molecular weight (Mw): 30,000).
5.00 g (carboxyl group amount: 17.5 mmol) of the obtained [Copolymer R-1] was weighed, and 7.36 g (tetraethylammonium hydroxide) of 35% by mass concentration of tetraethylammonium hydroxide aqueous solution (manufactured by Tokyo Chemical Industry Co., Ltd.). An ion content of 17.5 mmol) and 37.64 g of ion-exchanged water were added and mixed and stirred to prepare a 10% by mass aqueous solution of [Copolymer R-1].

[Synthesis of Copolymer R-2]
24.77 g (52.7 mmol) of methoxypolyethylene glycol acrylate (Blenmer AME-400, manufactured by NOF Corporation) and 11.26 g (26.3 mmol) of [Monomer M-1] were dissolved in 75 mL of dry methyl ethyl ketone. A monomer solution was prepared. After heating 10% of the monomer solution to 75 ° C. under an argon stream, 0.59 g (3.61 mmol) of 2,2′-azoiso (butyronitrile) (manufactured by Tokyo Chemical Industry Co., Ltd.) was dissolved in the remaining monomer solution. Was added dropwise over 1.5 hours and stirred at 75 ° C. for 4 hours. After cooling to room temperature, the resulting reaction solution was dropped into hexane. The precipitated copolymer was filtered off and dried under reduced pressure to obtain 34.23 g of [Copolymer R-2] (weight average molecular weight (Mw): 40,000).
45.00 g of ion-exchanged water was added to 5.00 g of the obtained [Copolymer R-2], mixed and stirred to prepare a 10% by mass aqueous solution of [Copolymer R-2].

[Synthesis of Copolymer R-3]
59.8 g (140 mmol) of [Monomer M-1] was dissolved in 2.02 g (28.0 mmol) of acrylic acid, 100 g of ion-exchanged water, 3.00 g of Aqualon KH-10 (Daiichi Kogyo Seiyaku Co., Ltd.) Of anionic radical reactive surfactant) and 1.00 g of ammonium persulfate were added to form a pre-emulsion with a homomixer. Next, 2.00 g of Aqualon KH-10 was added to 100 g of ion-exchanged water, heated to 80 ° C. under an argon stream, 10% of the pre-emulsion was added, and initial polymerization was performed for 30 minutes.
Next, the remaining pre-emulsion was polymerized while dropping over 2 hours, and then further polymerized at 80 ° C. for 2 hours. After cooling, the mixture is filtered and neutralized with aqueous ammonia to obtain a dispersion of a copolymer R-3 (weight average molecular weight (Mw): 21000, number average molecular weight (Mn): 9700) having a solid concentration of 30%. It was.

<Preparation of pigment dispersion>
(Preparation Example 1)
[Preparation of Black Pigment Dispersion PD-1]
10.0 parts of carbon black (NIPEX 160, manufactured by Degussa and 44.0 parts of ion-exchanged water were added to 40.0 parts of a 10% by weight aqueous solution of copolymer R-1, and stirred for 12 hours. Then, it was circulated and dispersed for 1 hour at a peripheral speed of 10 m / s using a disk type bead mill type KDL (manufactured by Shinmaru Enterprises Co., Ltd.) At this time, a zirconia ball having a diameter of 0.3 mm was used as a medium. Further, after filtration through a membrane filter having a pore size of 1.2 μm, ion exchange water was added so that the pigment concentration was 16% by mass to obtain a black pigment dispersion PD-1.

(Preparation Example 2)
[Preparation of Black Pigment Dispersion PD-2]
The same procedure as for Pigment Dispersion PD-1, except that a 10% by weight aqueous solution of 40.0 parts of copolymer R-2 was used instead of the 10% by weight aqueous solution of 40.0 parts of copolymer R-1. Thus, a black pigment dispersion PD-2 having a pigment concentration of 16% by mass was obtained.

(Preparation Example 3)
[Preparation of Black Pigment Dispersion PD-3]
40.0 parts of 10% by weight aqueous solution of copolymer R-1 and 44.0 parts of ion-exchanged water instead of 16.0 parts of wetting and dispersing agent byk190 (by Big Chemie, solid content 40% by weight) and 68 A pigment dispersion PD-3 having a pigment concentration of 16% by mass was obtained in the same manner as in the pigment dispersion PD-1, except that 0.0 part of ion-exchanged water was used.
In addition, about the said wet dispersing agent byk190 (the Big Chemie company make, solid content of 40 mass%) is diluted 300 times with ion-exchange water, and the absorption spectrum of the ultraviolet visible region of this diluted solution is measured with a spectrophotometer UH-3900H. As a result, since a peak of naphthyl group near 284 nm was not detected, it was confirmed that no naphthyl group was present. Therefore, the wetting and dispersing agent byk190 does not have the structural unit represented by the general formula (1).

(Preparation Example 4)
[Preparation of Cyan Pigment Dispersion PD-4]
A cyan pigment dispersion having a pigment concentration of 16% by mass in the same manner as pigment dispersion PD-1, except that Pigment Blue 15: 3 (Dainipei Seika Co., Ltd., Chromofine Blue) was used instead of carbon black. PD-4 was obtained.

(Preparation Example 5)
[Preparation of Magenta Pigment Dispersion PD-5]
A magenta pigment dispersion PD-5 having a pigment concentration of 16% by mass was prepared in the same manner as the pigment dispersion PD-1, except that Pigment Red 122 (manufactured by Clariant, Toner Magenta EO02) was used instead of carbon black. Obtained.

(Preparation Example 6)
[Preparation of Yellow Pigment Dispersion PD-6]
Yellow Pigment Dispersion PD- with a pigment concentration of 16% by mass in the same manner as Pigment Dispersion PD-1, except that Pigment Yellow 74 (First Yellow 531 manufactured by Dainichi Seika Co., Ltd.) was used instead of carbon black. 6 was obtained.

<Preparation of water-dispersible resin dispersion>
(Preparation Example 7)
-Preparation of resin fine particle dispersion 1-
After the inside of a 1 L flask equipped with a mechanical stirrer, thermometer, nitrogen gas inlet tube, reflux tube, and dropping funnel was sufficiently substituted with nitrogen gas, 8.0 g of Latemul S-180 (Kao) was added to 350 g of ion-exchanged water. (Reactive anionic surfactant) manufactured by the company was added and mixed, and the temperature was raised to 65 ° C. Next, 3.0 g of reaction initiator t-butyl peroxobenzoate and 1.0 g of sodium isoascorbate were added, and after 5 minutes, 45 g of methyl methacrylate, 160 g of 2-ethylhexyl methacrylate, 5 g of acrylic acid, 45 g of butyl methacrylate Then, a mixture of 30 g of cyclohexyl methacrylate, 15 g of vinyltriethoxysilane, 8.0 g of Latemul S-180, and 340 g of ion-exchanged water was added dropwise over 3 hours. Subsequently, after heat-aging at 80 degreeC for 2 hours, it cooled to normal temperature and adjusted pH to 7-8 with sodium hydroxide. Subsequently, ethanol was distilled off by an evaporator and the water content was adjusted to obtain 730 g of an acrylic-silicone polymer fine particle dispersion having a solid content of 40%. The volume average particle size (D ₅₀ ) of the polymer fine particles in the dispersion was 125 nm as measured with a particle size distribution measuring device (Nikkiso Co., Ltd., Nanotrac UPA-EX150).

<Preparation of Inks I-1 to I-19 and Inks RI-1 to RI-3>
2. In a container equipped with a stirrer, 24.00 parts of 3-ethyl-3-hydroxymethyloxetane of formula (4-1), 5.00 parts of propylene glycol monopropyl ether, glycerin (SP value: 16.38) 00 parts, 5.00 parts of triethylene glycol (SP value: 15.40) and 2.00 parts of a surfactant “TEGO WET 270” were added and mixed and stirred for 30 minutes. Next, 40.00 parts of black pigment dispersion PD-1 of Preparation Example 1 and 16.00 parts of ion-exchanged water were added and mixed and stirred for 60 minutes. Furthermore, 5.00 parts of resin fine particle dispersion 1 was added and mixed and stirred for 30 minutes. The obtained mixture was filtered under pressure through a polyvinylidene fluoride membrane filter having an average pore size of 1.2 μm to remove coarse particles and dust, and ink I-1 was obtained.

  In the same manner as the ink I-1, the organic solvent X, the compound Z, and other solvents shown in the columns of Example inks I-2 to I-19 and Comparative inks RI-1 to RI-3 shown in Table 1-1 below. Then, the surfactant was mixed and stirred, then the pigment dispersion and ion-exchanged water were added and mixed, and the water-dispersible resin was further added and mixed and stirred. The obtained mixture was filtered under pressure with a polyvinylidene fluoride membrane filter having an average pore size of 1.2 μm to remove coarse particles and dust, and inks I-2 to I-19 and inks RI-1 to RI-3 were obtained. Obtained.

<Preparation of Inks II-1 to II-19 and Inks RII-1 to RII-3>
In a container equipped with a stirrer, 24.00 parts of 3-ethyl-3-hydroxymethyloxetane of the formula (4-1), 5.00 parts of propylene glycol monopropyl ether, 3.00 parts of glycerin, and 5. 5 of triethylene glycol. 00 parts, 0.67 part of a wax / water dispersion “AQUACER 531” (solid content: 45% by mass, manufactured by BYK) and 2.00 parts of a surfactant “TEGO WET 270” were added and mixed and stirred for 30 minutes. Next, 40.00 parts of the black pigment dispersion PD-1 of Preparation Example 1 and 15.33 parts of ion-exchanged water were added and mixed and stirred for 60 minutes. Furthermore, 5.00 parts of resin fine particle dispersion 1 was added and mixed and stirred for 30 minutes. The obtained mixture was filtered under pressure with a polyvinylidene fluoride membrane filter having an average pore size of 1.2 μm to remove coarse particles and dust to obtain ink II-1.

  In the same manner as Ink II-1, organic solvent X, compound Z, and other solvents shown in the columns of Example Inks II-2 to II-19 and Comparative Inks RII-1 to RII-3 in Table 1-2 below Then, the wax and the surfactant were mixed and stirred, then the pigment dispersion and ion-exchanged water were added and mixed, and the water-dispersible resin was further added and mixed and stirred. The obtained mixture was filtered under pressure with a polyvinylidene fluoride membrane filter having an average pore size of 1.2 μm to remove coarse particles and dust, and inks II-2 to II-19 and inks RII-1 to RII-3 were obtained. Obtained.

The details in Table 1-1 and Table 1-2 are as follows.
・ AQUACER531: Polyethylene wax
(BYK, melting point 130 ° C., active ingredient 45%)
・ AQUACER 515: Polyethylene wax
(BYK, melting point 135 ° C, active ingredient 35%)
・ Cerosol 524: Carnauba wax
(Manufactured by Chukyo Yushi Co., Ltd., melting point 83 ° C, active ingredient 30%)
・ Nopcoat PEM-17: Polyolefin wax
(San Nopco, melting point 105 ° C, active ingredient 40%)
・ HYTEC E-8237: Polypropylene wax
(Toho Chemical Co., Ltd., melting point 106 ° C, active ingredient 40%)
・ HYTEC P-9018: Polypropylene wax
(Toho Chemical Co., Ltd., melting point 156 ° C., active ingredient 35%)
-TEGO Wet 270: Polyether-modified siloxane compound
(Evonik 100% active ingredient)
・ Unidyne DSN403N: Polyoxyethylene perfluoroalkyl ether
(Daikin Industries, 100% active ingredient)

[Examples I-1 to 19, Comparative Examples I-1 to 4, and Examples II-1 to 19, Comparative Examples II-1 to 4]
For each of the inks used in Examples I-1 to 19 and Comparative Examples I-2 to 4, Example II-1 to 19 and Comparative Examples II-2 to 4, parameters relating to the solvent and physical properties measured as described below were used. The results are shown in Tables 2-1 and 2-2. The ink used in Comparative Example I-1 and Comparative Example II-1 is the same as Ink I-1 used in Example I-1 and Ink II-1 used in Example II-1, respectively. 2-1, not shown in Table 2-2.
<Dynamic surface tension>
The dynamic surface tension at the surface lifetime of 15 msec according to the maximum bubble pressure method was measured at 25 ° C. using SITA DynoTester (manufactured by SITA).
<Static surface tension>
It measured at 25 degreeC using the automatic surface tension meter (DY-300, product made by Kyowa Interface Science).

In Examples I-1 to 19 and Comparative Examples I-2 to I-4, each ink described in Table 2-1 was used, images were formed using an apparatus using the following circulation type head, and the characteristics were evaluated. The results are shown in Table 3-1.
<Ink ejection device using circulating head>
Each ink listed in Table 2-1 is set on an ink jet printer (Ricoh's IPSiO GX-e5500 modified machine) equipped with the circulation type head shown in FIGS. The operation of printing 1000 sheets was performed. After 24 hours from the end of printing, the following beading, drying properties, continuous ejection reliability, and maintenance ink consumption were evaluated. Evaluation criteria are shown below. During this evaluation, the ink was always circulated regardless of the operation / pause of the circulation type discharge head. The results are shown as Examples I-1 to 19 and Comparative Examples I-2 to 4 in Table 3-1.

<Ink ejection device that does not use a circulating head>
The ink I-1 was set in a commercially available ink jet printer (IPSiO GX-e5500, manufactured by Ricoh Co., Ltd.) equipped with a non-recyclable head, and an operation of printing 1000 print charts with a print area of 5% was performed. After 24 hours from the end of printing, the following beading, drying properties, continuous ejection reliability, and maintenance ink consumption were evaluated. Evaluation criteria are shown below. The results are shown as Comparative Example I-1 in Table 3-1.

<Beading>
The recording medium 1 (OK top coat + US basis weight 104.7 g / m ² (manufactured by Oji Paper Co., Ltd.)) and the recording medium 2 (Lumiart gloss 90 gsm) were ejected at 300 dpi × 300 dpi and 4.0 pL per pixel. The beading of the solid image of 5 cm × 5 cm formed in (MONDI Color Copy) was visually confirmed and evaluated according to the following criteria.
〔Evaluation criteria〕
AA: None at all A: Very little, visible from a distance of 15 cm,
A beading that is not visible from a distance of 50 cm B: Slightly, visible from a distance of 50 cm,
Beading that cannot be seen from a distance of 1 m C: Beading that is intense and visible from a distance of 1 m

<Drying>
Similar to the above <Beading> evaluation, solid images were printed on two types of recording media, and then the printing portion was dried for 30 seconds in a thermostatic bath set so that the internal temperature was 100 ° C. Immediately after that, an unprinted paper (4 cm × 4 cm) is overlaid on the printing portion, and a rubber sheet of 2 cm in length × 2 cm in width × 0.2 cm in thickness is arranged on the center of the paper. A weight was placed on the rubber sheet so that the pressure applied to the pressure was 0.5 kgf / cm ^2, and left under an environment of 23 ° C. and 50% RH for 12 hours. After standing, the overlapped paper was peeled off, and the transfer of the pigment onto the unprinted paper was visually observed, and the transferability was evaluated according to the following evaluation criteria.
〔Evaluation criteria〕
AA: Little transfer of pigment to paper, no sticking between papers A: Little transfer of pigment to paper, but sticking between papers B: Slightly to paper Transfer of pigment is seen (transfer of less than 10% of the total paper area)
C: Clear pigment transfer to paper (area transfer of 10% or more of the entire paper)

<Continuous discharge reliability>
Using the ink ejection device, the liquid droplets were discarded from all the nozzles for 1 hour.
After 1 hour, print a nozzle check pattern on glossy inkjet paper (Painted Photo Finishing Value, manufactured by FUJIFILM Corporation) and check the number of ejection nozzles from which ink was ejected against the total number of nozzles 384. Evaluation was made according to the following criteria.
[Evaluation criteria]
A: The number of discharge nozzles is 368 or more (a level that causes no problem in actual use)
B: The number of discharge nozzles is 192 or more and less than 368 C: The number of discharge nozzles is less than 192

<Maintenance ink consumption>
Using the ink discharge device, the ink was left in a constant temperature bath at 50 ° C. for 1 week. Then, a nozzle check pattern is printed on glossy ink jet paper (Painted Photo Finishing Value, manufactured by FUJIFILM Corporation) to check for missing nozzles, and for 1 second with a suction pressure of −25 kPa · s from the suction cap. Ink was sucked. Then, a nozzle check pattern was printed again to confirm the state of nozzle missing. Suction and nozzle check pattern printing were repeated until nozzle missing was completely eliminated. At this time, the maintenance ink consumption required until the nozzle completely recovered was evaluated as the number of suctions based on the following criteria.
A: Completely recovered with 0 suction (no nozzle missing after standing) or 1 suction B: Completely recovered with 2 or more and 5 or less suction C: Completely recovered or not fully recovered with 6 or more suctions

<Evaluation of scratch resistance>
Similar to the above <Beading> evaluation, solid images were printed on two types of recording media, and then the printing portion was dried for 30 seconds in a thermostatic bath set so that the internal temperature was 100 ° C. Using a clock meter CM-1 (manufactured by Toyo Seiki Co., Ltd.), the printed portion of the image sample was rubbed with a white cotton cloth 5 times with a load of 900 g. Evaluation was performed according to the following evaluation criteria.
A: Visual dropout of the image and almost no stain around the image B: Little dropout of the image visually and little stain around the image C: Visual dropout of the image and stain around the image are remarkable

  From the comparison between Example I-1 and Comparative Example I-1, it can be seen that “continuous ejection reliability” and “maintenance ink consumption” are improved by using the circulation head. This is because the circulation type head constantly circulates the ink along the path, so that even if bubbles enter, it is discharged immediately. Presumed. In addition, since the ink in the vicinity of the nozzle is constantly circulated, local thickening of the nozzle portion does not occur, and it is not necessary to discard the ink, leading to a reduction in “maintenance ink consumption”.

In Examples II-1 to 19 and Comparative Examples II-2 to II-4, each ink described in Table 2-2 was used, and an image was formed by an apparatus using a circulation type head similar to Example I-1. The characteristics were evaluated in the same manner as in Example I-1.
Comparative Example II-1 uses ink II-1 and, like Comparative Example I-1, forms an image using an ink ejection device that does not use a circulating head, and exhibits the same characteristics as Comparative Example I-1. evaluated.
The results are shown in Table 3-2.

(About FIGS. 1-2)
400 Image forming apparatus 401 Exterior of image forming apparatus 401c Cover of apparatus main body 404 Cartridge holder 410 Main tank 410k, 410c, 410m, 410y For each color of black (K), cyan (C), magenta (M), yellow (Y) Main tank 411 Ink storage section 413 Ink discharge port 414 Storage container case 420 Mechanism section 434 Discharge head 436 Supply tube

(About FIGS. 3 to 8)
DESCRIPTION OF SYMBOLS 1 Nozzle plate 2 Flow path plate 3 Vibration board member 4 Nozzle 6 Individual liquid chamber 6a, 6b, 6c, 6d, 6e Through-groove part which comprises individual liquid chamber 7 Fluid resistance part 7a Through-groove part which comprises fluid resistance part 8 Liquid introduction 8a, 8b Through-groove part constituting liquid introduction part 9 Filter part 10 Common liquid chamber 10A Downstream-side common liquid chamber 10a Through-groove part 10B Upstream-side common liquid chamber 10b Groove part 11 Piezoelectric actuator 12 Piezoelectric member 12A, 12B Piezoelectric element 13 Base member DESCRIPTION OF SYMBOLS 15 Flexible wiring member 20 Common liquid chamber member 21 1st common liquid chamber member 22 2nd common liquid chamber member 25a, 25b Through-hole for piezoelectric actuators 30 Vibration area 30a, 30b Protrusion part 40 Flow path member 41-45 Plate-shaped member 50 Circulation common liquid chamber 50a Groove 51 Fluid resistance 51a Through groove 52, 53 constituting the fluid resistance 52a, 52b Through-groove parts constituting the circulation flow path 53a, 53b, 53c, 53d Through-groove parts constituting the circulation flow path 71 Supply port 71a Through-hole 81 Circulation port 81a, 81b Through-hole

(About FIGS. 10-12)
401 Guide member 403 Carriage 404 Ink discharge head 405 Main scanning motor 406 Drive pulley 407 Driven pulley 408 Timing belt 410 Paper 412 Conveying belt 413 Conveying roller 414 Tension roller 416 Sub-scanning motor 417 Timing belt 418 Timing pulley 420 Maintenance / recovery mechanism 421 Cap member 422 Wiper member 440 Ink discharge unit 491A, 491B Side plate 491C Back plate 493 Main scanning movement mechanism 494 Supply / circulation mechanism 495 Conveyance mechanism

(About Figure 13)
DESCRIPTION OF SYMBOLS 1 Recording medium 2 Ink discharge part 3 Conveyor belt 4 Hot air drying apparatus 5 Image formation part 6 Drying process part 7 Transfer roll

Japanese Patent Laying-Open No. 2015-71289 JP 2007-91908 A

Claims (12)

Ink, a nozzle for ejecting the ink, a plurality of individual liquid chambers communicating with the nozzle, an inflow channel for allowing the ink to flow into the individual liquid chamber, and an outflow channel for allowing the ink to flow out from the individual liquid chamber An ink discharge device comprising: an ink discharge head, wherein the ink flowing out from the outflow passage flows into the inflow passage and circulates;
The ink contains an organic solvent X having a solubility parameter (SP value) of 8.9 or more and 12.0 or less excluding water, a coloring material, and a glycol ether compound, and a copolymer.
The copolymer has a structural unit represented by the following general formula (1),
The ink discharge apparatus includes a negative pressure generating unit that generates a negative pressure that causes the ink to flow out of the individual liquid chamber.
(In the above formula, R1 represents a hydrogen atom or a methyl group. Y represents an alkylene group having 2 to 18 carbon atoms.) The ink ejection apparatus according to claim 1, wherein the copolymer further has a structural unit represented by the following general formula (2).
(In the above formula, R2 represents a hydrogen atom or a methyl group. M represents a hydrogen atom, an alkali metal or organic ammonium.)   The ratio of the content of the organic solvent X contained in the ink to the total content of water and the organic solvent X contained in the ink {organic solvent X / (organic solvent X + water)} is 20% by mass or more. The ink ejection device according to 1 or 2.   The ink discharge apparatus according to any one of claims 1 to 3, wherein the ink includes a glycol ether compound (compound Z) having a vapor pressure of 50 mmHg or more in an environment of 100 ° C.   The ink discharge apparatus according to claim 4, wherein the compound Z is at least one selected from propylene glycol monopropyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and propylene glycol monobutyl ether.   The ink ejection apparatus according to claim 4 or 5, wherein a ratio (mass ratio) of the content of the organic solvent X and the compound Z is 1: 1 to 8: 1. The ink discharge apparatus according to claim 1, wherein the organic solvent X is at least one selected from compounds represented by the following general formula (3), general formula (4), and formula (5). .
(In the above formula, R3 represents an alkyl group having 4 to 6 carbon atoms.)
(In the above formula, R4 represents an alkyl group having 1 to 2 carbon atoms.)
  The ink contains a wax, and a mass ratio (x / w) of the content x of the organic solvent X to the content w of the wax in the ink satisfies 30 ≦ x / w ≦ 500. The ink ejection device according to any one of the above.   The ink discharge apparatus according to claim 8, wherein the wax has a melting point of 100 ° C. to 140 ° C.   The ink ejection device according to claim 1, wherein the ink contains a polyether-modified siloxane compound.   11. The ink according to claim 1, wherein the ink has a static surface tension of 20 mN / m or more and a dynamic surface tension of 34 mN / m or less at a bubble lifetime of 15 msec by a maximum bubble pressure method. Ink ejection device. Ink, a nozzle for ejecting the ink, a plurality of individual liquid chambers communicating with the nozzle, an inflow channel for allowing the ink to flow into the individual liquid chamber, and an outflow channel for allowing the ink to flow out from the individual liquid chamber An ink ejection head, and an ink ejection device that circulates the ink flowing out from the outflow channel by flowing into the inflow channel,
The ink contains an organic solvent X having a solubility parameter (SP value) of 8.9 or more and 12.0 or less excluding water, a coloring material, and a glycol ether compound, and a copolymer.
The copolymer has a structural unit represented by the following general formula (1),
An ink discharge method comprising a negative pressure generating step of generating a negative pressure for causing the ink to flow out of the individual liquid chamber.
(In the above formula, R1 represents a hydrogen atom or a methyl group. Y represents an alkylene group having 2 to 18 carbon atoms.)